diff --git a/CMakeLists.txt b/CMakeLists.txt
index a7993d86c..43c68acfb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -162,6 +162,10 @@ macro (config_hook)
       opm_need_version_of ("dune-fem")
   endif()
   opm_need_version_of ("opm-models")
+
+  add_definitions(-DFMT_HEADER_ONLY)
+  list(APPEND EXTRA_INCLUDES SYSTEM ${PROJECT_SOURCE_DIR}/external/fmtlib/include)
+  include_directories(${EXTRA_INCLUDES})
 endmacro (config_hook)
 
 macro (prereqs_hook)
diff --git a/external/fmtlib/LICENSE.rst b/external/fmtlib/LICENSE.rst
new file mode 100644
index 000000000..f0ec3db4d
--- /dev/null
+++ b/external/fmtlib/LICENSE.rst
@@ -0,0 +1,27 @@
+Copyright (c) 2012 - present, Victor Zverovich
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+--- Optional exception to the license ---
+
+As an exception, if, as a result of your compiling your source code, portions
+of this Software are embedded into a machine-executable object form of such
+source code, you may redistribute such embedded portions in such object form
+without including the above copyright and permission notices.
diff --git a/external/fmtlib/README.opm b/external/fmtlib/README.opm
new file mode 100644
index 000000000..ee971f32c
--- /dev/null
+++ b/external/fmtlib/README.opm
@@ -0,0 +1,12 @@
+The include/ directory is a copy of the include directory from version 7.0.3 of
+the fmtlib distribution. The fmtlib can be found at https://github.com/fmtlib/fmt
+
+The fmtlib code embedded here should be compiled in header only mode, to ensure
+that the symbol FMT_HEADER_ONLY must be defined before the the fmt/format.h
+header is included:
+
+   #define FMT_HEADER_ONLY
+   #include <fmt/format.h>
+   
+   ....
+   auto msg = fmt::format("Hello {}", "world");
\ No newline at end of file
diff --git a/external/fmtlib/include/fmt/chrono.h b/external/fmtlib/include/fmt/chrono.h
new file mode 100644
index 000000000..e70b8053a
--- /dev/null
+++ b/external/fmtlib/include/fmt/chrono.h
@@ -0,0 +1,1123 @@
+// Formatting library for C++ - chrono support
+//
+// Copyright (c) 2012 - present, Victor Zverovich
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+#ifndef FMT_CHRONO_H_
+#define FMT_CHRONO_H_
+
+#include <chrono>
+#include <ctime>
+#include <locale>
+#include <sstream>
+
+#include "format.h"
+#include "locale.h"
+
+FMT_BEGIN_NAMESPACE
+
+// Enable safe chrono durations, unless explicitly disabled.
+#ifndef FMT_SAFE_DURATION_CAST
+#  define FMT_SAFE_DURATION_CAST 1
+#endif
+#if FMT_SAFE_DURATION_CAST
+
+// For conversion between std::chrono::durations without undefined
+// behaviour or erroneous results.
+// This is a stripped down version of duration_cast, for inclusion in fmt.
+// See https://github.com/pauldreik/safe_duration_cast
+//
+// Copyright Paul Dreik 2019
+namespace safe_duration_cast {
+
+template <typename To, typename From,
+          FMT_ENABLE_IF(!std::is_same<From, To>::value &&
+                        std::numeric_limits<From>::is_signed ==
+                            std::numeric_limits<To>::is_signed)>
+FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
+  ec = 0;
+  using F = std::numeric_limits<From>;
+  using T = std::numeric_limits<To>;
+  static_assert(F::is_integer, "From must be integral");
+  static_assert(T::is_integer, "To must be integral");
+
+  // A and B are both signed, or both unsigned.
+  if (F::digits <= T::digits) {
+    // From fits in To without any problem.
+  } else {
+    // From does not always fit in To, resort to a dynamic check.
+    if (from < (T::min)() || from > (T::max)()) {
+      // outside range.
+      ec = 1;
+      return {};
+    }
+  }
+  return static_cast<To>(from);
+}
+
+/**
+ * converts From to To, without loss. If the dynamic value of from
+ * can't be converted to To without loss, ec is set.
+ */
+template <typename To, typename From,
+          FMT_ENABLE_IF(!std::is_same<From, To>::value &&
+                        std::numeric_limits<From>::is_signed !=
+                            std::numeric_limits<To>::is_signed)>
+FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
+  ec = 0;
+  using F = std::numeric_limits<From>;
+  using T = std::numeric_limits<To>;
+  static_assert(F::is_integer, "From must be integral");
+  static_assert(T::is_integer, "To must be integral");
+
+  if (F::is_signed && !T::is_signed) {
+    // From may be negative, not allowed!
+    if (fmt::detail::is_negative(from)) {
+      ec = 1;
+      return {};
+    }
+
+    // From is positive. Can it always fit in To?
+    if (F::digits <= T::digits) {
+      // yes, From always fits in To.
+    } else {
+      // from may not fit in To, we have to do a dynamic check
+      if (from > static_cast<From>((T::max)())) {
+        ec = 1;
+        return {};
+      }
+    }
+  }
+
+  if (!F::is_signed && T::is_signed) {
+    // can from be held in To?
+    if (F::digits < T::digits) {
+      // yes, From always fits in To.
+    } else {
+      // from may not fit in To, we have to do a dynamic check
+      if (from > static_cast<From>((T::max)())) {
+        // outside range.
+        ec = 1;
+        return {};
+      }
+    }
+  }
+
+  // reaching here means all is ok for lossless conversion.
+  return static_cast<To>(from);
+
+}  // function
+
+template <typename To, typename From,
+          FMT_ENABLE_IF(std::is_same<From, To>::value)>
+FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
+  ec = 0;
+  return from;
+}  // function
+
+// clang-format off
+/**
+ * converts From to To if possible, otherwise ec is set.
+ *
+ * input                            |    output
+ * ---------------------------------|---------------
+ * NaN                              | NaN
+ * Inf                              | Inf
+ * normal, fits in output           | converted (possibly lossy)
+ * normal, does not fit in output   | ec is set
+ * subnormal                        | best effort
+ * -Inf                             | -Inf
+ */
+// clang-format on
+template <typename To, typename From,
+          FMT_ENABLE_IF(!std::is_same<From, To>::value)>
+FMT_CONSTEXPR To safe_float_conversion(const From from, int& ec) {
+  ec = 0;
+  using T = std::numeric_limits<To>;
+  static_assert(std::is_floating_point<From>::value, "From must be floating");
+  static_assert(std::is_floating_point<To>::value, "To must be floating");
+
+  // catch the only happy case
+  if (std::isfinite(from)) {
+    if (from >= T::lowest() && from <= (T::max)()) {
+      return static_cast<To>(from);
+    }
+    // not within range.
+    ec = 1;
+    return {};
+  }
+
+  // nan and inf will be preserved
+  return static_cast<To>(from);
+}  // function
+
+template <typename To, typename From,
+          FMT_ENABLE_IF(std::is_same<From, To>::value)>
+FMT_CONSTEXPR To safe_float_conversion(const From from, int& ec) {
+  ec = 0;
+  static_assert(std::is_floating_point<From>::value, "From must be floating");
+  return from;
+}
+
+/**
+ * safe duration cast between integral durations
+ */
+template <typename To, typename FromRep, typename FromPeriod,
+          FMT_ENABLE_IF(std::is_integral<FromRep>::value),
+          FMT_ENABLE_IF(std::is_integral<typename To::rep>::value)>
+To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
+                      int& ec) {
+  using From = std::chrono::duration<FromRep, FromPeriod>;
+  ec = 0;
+  // the basic idea is that we need to convert from count() in the from type
+  // to count() in the To type, by multiplying it with this:
+  struct Factor
+      : std::ratio_divide<typename From::period, typename To::period> {};
+
+  static_assert(Factor::num > 0, "num must be positive");
+  static_assert(Factor::den > 0, "den must be positive");
+
+  // the conversion is like this: multiply from.count() with Factor::num
+  // /Factor::den and convert it to To::rep, all this without
+  // overflow/underflow. let's start by finding a suitable type that can hold
+  // both To, From and Factor::num
+  using IntermediateRep =
+      typename std::common_type<typename From::rep, typename To::rep,
+                                decltype(Factor::num)>::type;
+
+  // safe conversion to IntermediateRep
+  IntermediateRep count =
+      lossless_integral_conversion<IntermediateRep>(from.count(), ec);
+  if (ec) {
+    return {};
+  }
+  // multiply with Factor::num without overflow or underflow
+  if (Factor::num != 1) {
+    const auto max1 = detail::max_value<IntermediateRep>() / Factor::num;
+    if (count > max1) {
+      ec = 1;
+      return {};
+    }
+    const auto min1 =
+        (std::numeric_limits<IntermediateRep>::min)() / Factor::num;
+    if (count < min1) {
+      ec = 1;
+      return {};
+    }
+    count *= Factor::num;
+  }
+
+  // this can't go wrong, right? den>0 is checked earlier.
+  if (Factor::den != 1) {
+    count /= Factor::den;
+  }
+  // convert to the to type, safely
+  using ToRep = typename To::rep;
+  const ToRep tocount = lossless_integral_conversion<ToRep>(count, ec);
+  if (ec) {
+    return {};
+  }
+  return To{tocount};
+}
+
+/**
+ * safe duration_cast between floating point durations
+ */
+template <typename To, typename FromRep, typename FromPeriod,
+          FMT_ENABLE_IF(std::is_floating_point<FromRep>::value),
+          FMT_ENABLE_IF(std::is_floating_point<typename To::rep>::value)>
+To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
+                      int& ec) {
+  using From = std::chrono::duration<FromRep, FromPeriod>;
+  ec = 0;
+  if (std::isnan(from.count())) {
+    // nan in, gives nan out. easy.
+    return To{std::numeric_limits<typename To::rep>::quiet_NaN()};
+  }
+  // maybe we should also check if from is denormal, and decide what to do about
+  // it.
+
+  // +-inf should be preserved.
+  if (std::isinf(from.count())) {
+    return To{from.count()};
+  }
+
+  // the basic idea is that we need to convert from count() in the from type
+  // to count() in the To type, by multiplying it with this:
+  struct Factor
+      : std::ratio_divide<typename From::period, typename To::period> {};
+
+  static_assert(Factor::num > 0, "num must be positive");
+  static_assert(Factor::den > 0, "den must be positive");
+
+  // the conversion is like this: multiply from.count() with Factor::num
+  // /Factor::den and convert it to To::rep, all this without
+  // overflow/underflow. let's start by finding a suitable type that can hold
+  // both To, From and Factor::num
+  using IntermediateRep =
+      typename std::common_type<typename From::rep, typename To::rep,
+                                decltype(Factor::num)>::type;
+
+  // force conversion of From::rep -> IntermediateRep to be safe,
+  // even if it will never happen be narrowing in this context.
+  IntermediateRep count =
+      safe_float_conversion<IntermediateRep>(from.count(), ec);
+  if (ec) {
+    return {};
+  }
+
+  // multiply with Factor::num without overflow or underflow
+  if (Factor::num != 1) {
+    constexpr auto max1 = detail::max_value<IntermediateRep>() /
+                          static_cast<IntermediateRep>(Factor::num);
+    if (count > max1) {
+      ec = 1;
+      return {};
+    }
+    constexpr auto min1 = std::numeric_limits<IntermediateRep>::lowest() /
+                          static_cast<IntermediateRep>(Factor::num);
+    if (count < min1) {
+      ec = 1;
+      return {};
+    }
+    count *= static_cast<IntermediateRep>(Factor::num);
+  }
+
+  // this can't go wrong, right? den>0 is checked earlier.
+  if (Factor::den != 1) {
+    using common_t = typename std::common_type<IntermediateRep, intmax_t>::type;
+    count /= static_cast<common_t>(Factor::den);
+  }
+
+  // convert to the to type, safely
+  using ToRep = typename To::rep;
+
+  const ToRep tocount = safe_float_conversion<ToRep>(count, ec);
+  if (ec) {
+    return {};
+  }
+  return To{tocount};
+}
+}  // namespace safe_duration_cast
+#endif
+
+// Prevents expansion of a preceding token as a function-style macro.
+// Usage: f FMT_NOMACRO()
+#define FMT_NOMACRO
+
+namespace detail {
+inline null<> localtime_r FMT_NOMACRO(...) { return null<>(); }
+inline null<> localtime_s(...) { return null<>(); }
+inline null<> gmtime_r(...) { return null<>(); }
+inline null<> gmtime_s(...) { return null<>(); }
+}  // namespace detail
+
+// Thread-safe replacement for std::localtime
+inline std::tm localtime(std::time_t time) {
+  struct dispatcher {
+    std::time_t time_;
+    std::tm tm_;
+
+    dispatcher(std::time_t t) : time_(t) {}
+
+    bool run() {
+      using namespace fmt::detail;
+      return handle(localtime_r(&time_, &tm_));
+    }
+
+    bool handle(std::tm* tm) { return tm != nullptr; }
+
+    bool handle(detail::null<>) {
+      using namespace fmt::detail;
+      return fallback(localtime_s(&tm_, &time_));
+    }
+
+    bool fallback(int res) { return res == 0; }
+
+#if !FMT_MSC_VER
+    bool fallback(detail::null<>) {
+      using namespace fmt::detail;
+      std::tm* tm = std::localtime(&time_);
+      if (tm) tm_ = *tm;
+      return tm != nullptr;
+    }
+#endif
+  };
+  dispatcher lt(time);
+  // Too big time values may be unsupported.
+  if (!lt.run()) FMT_THROW(format_error("time_t value out of range"));
+  return lt.tm_;
+}
+
+// Thread-safe replacement for std::gmtime
+inline std::tm gmtime(std::time_t time) {
+  struct dispatcher {
+    std::time_t time_;
+    std::tm tm_;
+
+    dispatcher(std::time_t t) : time_(t) {}
+
+    bool run() {
+      using namespace fmt::detail;
+      return handle(gmtime_r(&time_, &tm_));
+    }
+
+    bool handle(std::tm* tm) { return tm != nullptr; }
+
+    bool handle(detail::null<>) {
+      using namespace fmt::detail;
+      return fallback(gmtime_s(&tm_, &time_));
+    }
+
+    bool fallback(int res) { return res == 0; }
+
+#if !FMT_MSC_VER
+    bool fallback(detail::null<>) {
+      std::tm* tm = std::gmtime(&time_);
+      if (tm) tm_ = *tm;
+      return tm != nullptr;
+    }
+#endif
+  };
+  dispatcher gt(time);
+  // Too big time values may be unsupported.
+  if (!gt.run()) FMT_THROW(format_error("time_t value out of range"));
+  return gt.tm_;
+}
+
+namespace detail {
+inline size_t strftime(char* str, size_t count, const char* format,
+                       const std::tm* time) {
+  return std::strftime(str, count, format, time);
+}
+
+inline size_t strftime(wchar_t* str, size_t count, const wchar_t* format,
+                       const std::tm* time) {
+  return std::wcsftime(str, count, format, time);
+}
+}  // namespace detail
+
+template <typename Char> struct formatter<std::tm, Char> {
+  template <typename ParseContext>
+  auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    auto it = ctx.begin();
+    if (it != ctx.end() && *it == ':') ++it;
+    auto end = it;
+    while (end != ctx.end() && *end != '}') ++end;
+    tm_format.reserve(detail::to_unsigned(end - it + 1));
+    tm_format.append(it, end);
+    tm_format.push_back('\0');
+    return end;
+  }
+
+  template <typename FormatContext>
+  auto format(const std::tm& tm, FormatContext& ctx) -> decltype(ctx.out()) {
+    basic_memory_buffer<Char> buf;
+    size_t start = buf.size();
+    for (;;) {
+      size_t size = buf.capacity() - start;
+      size_t count = detail::strftime(&buf[start], size, &tm_format[0], &tm);
+      if (count != 0) {
+        buf.resize(start + count);
+        break;
+      }
+      if (size >= tm_format.size() * 256) {
+        // If the buffer is 256 times larger than the format string, assume
+        // that `strftime` gives an empty result. There doesn't seem to be a
+        // better way to distinguish the two cases:
+        // https://github.com/fmtlib/fmt/issues/367
+        break;
+      }
+      const size_t MIN_GROWTH = 10;
+      buf.reserve(buf.capacity() + (size > MIN_GROWTH ? size : MIN_GROWTH));
+    }
+    return std::copy(buf.begin(), buf.end(), ctx.out());
+  }
+
+  basic_memory_buffer<Char> tm_format;
+};
+
+namespace detail {
+template <typename Period> FMT_CONSTEXPR const char* get_units() {
+  return nullptr;
+}
+template <> FMT_CONSTEXPR const char* get_units<std::atto>() { return "as"; }
+template <> FMT_CONSTEXPR const char* get_units<std::femto>() { return "fs"; }
+template <> FMT_CONSTEXPR const char* get_units<std::pico>() { return "ps"; }
+template <> FMT_CONSTEXPR const char* get_units<std::nano>() { return "ns"; }
+template <> FMT_CONSTEXPR const char* get_units<std::micro>() { return "µs"; }
+template <> FMT_CONSTEXPR const char* get_units<std::milli>() { return "ms"; }
+template <> FMT_CONSTEXPR const char* get_units<std::centi>() { return "cs"; }
+template <> FMT_CONSTEXPR const char* get_units<std::deci>() { return "ds"; }
+template <> FMT_CONSTEXPR const char* get_units<std::ratio<1>>() { return "s"; }
+template <> FMT_CONSTEXPR const char* get_units<std::deca>() { return "das"; }
+template <> FMT_CONSTEXPR const char* get_units<std::hecto>() { return "hs"; }
+template <> FMT_CONSTEXPR const char* get_units<std::kilo>() { return "ks"; }
+template <> FMT_CONSTEXPR const char* get_units<std::mega>() { return "Ms"; }
+template <> FMT_CONSTEXPR const char* get_units<std::giga>() { return "Gs"; }
+template <> FMT_CONSTEXPR const char* get_units<std::tera>() { return "Ts"; }
+template <> FMT_CONSTEXPR const char* get_units<std::peta>() { return "Ps"; }
+template <> FMT_CONSTEXPR const char* get_units<std::exa>() { return "Es"; }
+template <> FMT_CONSTEXPR const char* get_units<std::ratio<60>>() {
+  return "m";
+}
+template <> FMT_CONSTEXPR const char* get_units<std::ratio<3600>>() {
+  return "h";
+}
+
+enum class numeric_system {
+  standard,
+  // Alternative numeric system, e.g. 十二 instead of 12 in ja_JP locale.
+  alternative
+};
+
+// Parses a put_time-like format string and invokes handler actions.
+template <typename Char, typename Handler>
+FMT_CONSTEXPR const Char* parse_chrono_format(const Char* begin,
+                                              const Char* end,
+                                              Handler&& handler) {
+  auto ptr = begin;
+  while (ptr != end) {
+    auto c = *ptr;
+    if (c == '}') break;
+    if (c != '%') {
+      ++ptr;
+      continue;
+    }
+    if (begin != ptr) handler.on_text(begin, ptr);
+    ++ptr;  // consume '%'
+    if (ptr == end) FMT_THROW(format_error("invalid format"));
+    c = *ptr++;
+    switch (c) {
+    case '%':
+      handler.on_text(ptr - 1, ptr);
+      break;
+    case 'n': {
+      const Char newline[] = {'\n'};
+      handler.on_text(newline, newline + 1);
+      break;
+    }
+    case 't': {
+      const Char tab[] = {'\t'};
+      handler.on_text(tab, tab + 1);
+      break;
+    }
+    // Day of the week:
+    case 'a':
+      handler.on_abbr_weekday();
+      break;
+    case 'A':
+      handler.on_full_weekday();
+      break;
+    case 'w':
+      handler.on_dec0_weekday(numeric_system::standard);
+      break;
+    case 'u':
+      handler.on_dec1_weekday(numeric_system::standard);
+      break;
+    // Month:
+    case 'b':
+      handler.on_abbr_month();
+      break;
+    case 'B':
+      handler.on_full_month();
+      break;
+    // Hour, minute, second:
+    case 'H':
+      handler.on_24_hour(numeric_system::standard);
+      break;
+    case 'I':
+      handler.on_12_hour(numeric_system::standard);
+      break;
+    case 'M':
+      handler.on_minute(numeric_system::standard);
+      break;
+    case 'S':
+      handler.on_second(numeric_system::standard);
+      break;
+    // Other:
+    case 'c':
+      handler.on_datetime(numeric_system::standard);
+      break;
+    case 'x':
+      handler.on_loc_date(numeric_system::standard);
+      break;
+    case 'X':
+      handler.on_loc_time(numeric_system::standard);
+      break;
+    case 'D':
+      handler.on_us_date();
+      break;
+    case 'F':
+      handler.on_iso_date();
+      break;
+    case 'r':
+      handler.on_12_hour_time();
+      break;
+    case 'R':
+      handler.on_24_hour_time();
+      break;
+    case 'T':
+      handler.on_iso_time();
+      break;
+    case 'p':
+      handler.on_am_pm();
+      break;
+    case 'Q':
+      handler.on_duration_value();
+      break;
+    case 'q':
+      handler.on_duration_unit();
+      break;
+    case 'z':
+      handler.on_utc_offset();
+      break;
+    case 'Z':
+      handler.on_tz_name();
+      break;
+    // Alternative representation:
+    case 'E': {
+      if (ptr == end) FMT_THROW(format_error("invalid format"));
+      c = *ptr++;
+      switch (c) {
+      case 'c':
+        handler.on_datetime(numeric_system::alternative);
+        break;
+      case 'x':
+        handler.on_loc_date(numeric_system::alternative);
+        break;
+      case 'X':
+        handler.on_loc_time(numeric_system::alternative);
+        break;
+      default:
+        FMT_THROW(format_error("invalid format"));
+      }
+      break;
+    }
+    case 'O':
+      if (ptr == end) FMT_THROW(format_error("invalid format"));
+      c = *ptr++;
+      switch (c) {
+      case 'w':
+        handler.on_dec0_weekday(numeric_system::alternative);
+        break;
+      case 'u':
+        handler.on_dec1_weekday(numeric_system::alternative);
+        break;
+      case 'H':
+        handler.on_24_hour(numeric_system::alternative);
+        break;
+      case 'I':
+        handler.on_12_hour(numeric_system::alternative);
+        break;
+      case 'M':
+        handler.on_minute(numeric_system::alternative);
+        break;
+      case 'S':
+        handler.on_second(numeric_system::alternative);
+        break;
+      default:
+        FMT_THROW(format_error("invalid format"));
+      }
+      break;
+    default:
+      FMT_THROW(format_error("invalid format"));
+    }
+    begin = ptr;
+  }
+  if (begin != ptr) handler.on_text(begin, ptr);
+  return ptr;
+}
+
+struct chrono_format_checker {
+  FMT_NORETURN void report_no_date() { FMT_THROW(format_error("no date")); }
+
+  template <typename Char> void on_text(const Char*, const Char*) {}
+  FMT_NORETURN void on_abbr_weekday() { report_no_date(); }
+  FMT_NORETURN void on_full_weekday() { report_no_date(); }
+  FMT_NORETURN void on_dec0_weekday(numeric_system) { report_no_date(); }
+  FMT_NORETURN void on_dec1_weekday(numeric_system) { report_no_date(); }
+  FMT_NORETURN void on_abbr_month() { report_no_date(); }
+  FMT_NORETURN void on_full_month() { report_no_date(); }
+  void on_24_hour(numeric_system) {}
+  void on_12_hour(numeric_system) {}
+  void on_minute(numeric_system) {}
+  void on_second(numeric_system) {}
+  FMT_NORETURN void on_datetime(numeric_system) { report_no_date(); }
+  FMT_NORETURN void on_loc_date(numeric_system) { report_no_date(); }
+  FMT_NORETURN void on_loc_time(numeric_system) { report_no_date(); }
+  FMT_NORETURN void on_us_date() { report_no_date(); }
+  FMT_NORETURN void on_iso_date() { report_no_date(); }
+  void on_12_hour_time() {}
+  void on_24_hour_time() {}
+  void on_iso_time() {}
+  void on_am_pm() {}
+  void on_duration_value() {}
+  void on_duration_unit() {}
+  FMT_NORETURN void on_utc_offset() { report_no_date(); }
+  FMT_NORETURN void on_tz_name() { report_no_date(); }
+};
+
+template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
+inline bool isnan(T) {
+  return false;
+}
+template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
+inline bool isnan(T value) {
+  return std::isnan(value);
+}
+
+template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
+inline bool isfinite(T) {
+  return true;
+}
+template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
+inline bool isfinite(T value) {
+  return std::isfinite(value);
+}
+
+// Converts value to int and checks that it's in the range [0, upper).
+template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
+inline int to_nonnegative_int(T value, int upper) {
+  FMT_ASSERT(value >= 0 && value <= upper, "invalid value");
+  (void)upper;
+  return static_cast<int>(value);
+}
+template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
+inline int to_nonnegative_int(T value, int upper) {
+  FMT_ASSERT(
+      std::isnan(value) || (value >= 0 && value <= static_cast<T>(upper)),
+      "invalid value");
+  (void)upper;
+  return static_cast<int>(value);
+}
+
+template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
+inline T mod(T x, int y) {
+  return x % static_cast<T>(y);
+}
+template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
+inline T mod(T x, int y) {
+  return std::fmod(x, static_cast<T>(y));
+}
+
+// If T is an integral type, maps T to its unsigned counterpart, otherwise
+// leaves it unchanged (unlike std::make_unsigned).
+template <typename T, bool INTEGRAL = std::is_integral<T>::value>
+struct make_unsigned_or_unchanged {
+  using type = T;
+};
+
+template <typename T> struct make_unsigned_or_unchanged<T, true> {
+  using type = typename std::make_unsigned<T>::type;
+};
+
+#if FMT_SAFE_DURATION_CAST
+// throwing version of safe_duration_cast
+template <typename To, typename FromRep, typename FromPeriod>
+To fmt_safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from) {
+  int ec;
+  To to = safe_duration_cast::safe_duration_cast<To>(from, ec);
+  if (ec) FMT_THROW(format_error("cannot format duration"));
+  return to;
+}
+#endif
+
+template <typename Rep, typename Period,
+          FMT_ENABLE_IF(std::is_integral<Rep>::value)>
+inline std::chrono::duration<Rep, std::milli> get_milliseconds(
+    std::chrono::duration<Rep, Period> d) {
+  // this may overflow and/or the result may not fit in the
+  // target type.
+#if FMT_SAFE_DURATION_CAST
+  using CommonSecondsType =
+      typename std::common_type<decltype(d), std::chrono::seconds>::type;
+  const auto d_as_common = fmt_safe_duration_cast<CommonSecondsType>(d);
+  const auto d_as_whole_seconds =
+      fmt_safe_duration_cast<std::chrono::seconds>(d_as_common);
+  // this conversion should be nonproblematic
+  const auto diff = d_as_common - d_as_whole_seconds;
+  const auto ms =
+      fmt_safe_duration_cast<std::chrono::duration<Rep, std::milli>>(diff);
+  return ms;
+#else
+  auto s = std::chrono::duration_cast<std::chrono::seconds>(d);
+  return std::chrono::duration_cast<std::chrono::milliseconds>(d - s);
+#endif
+}
+
+template <typename Rep, typename Period,
+          FMT_ENABLE_IF(std::is_floating_point<Rep>::value)>
+inline std::chrono::duration<Rep, std::milli> get_milliseconds(
+    std::chrono::duration<Rep, Period> d) {
+  using common_type = typename std::common_type<Rep, std::intmax_t>::type;
+  auto ms = mod(d.count() * static_cast<common_type>(Period::num) /
+                    static_cast<common_type>(Period::den) * 1000,
+                1000);
+  return std::chrono::duration<Rep, std::milli>(static_cast<Rep>(ms));
+}
+
+template <typename Char, typename Rep, typename OutputIt>
+OutputIt format_duration_value(OutputIt out, Rep val, int precision) {
+  const Char pr_f[] = {'{', ':', '.', '{', '}', 'f', '}', 0};
+  if (precision >= 0) return format_to(out, pr_f, val, precision);
+  const Char fp_f[] = {'{', ':', 'g', '}', 0};
+  const Char format[] = {'{', '}', 0};
+  return format_to(out, std::is_floating_point<Rep>::value ? fp_f : format,
+                   val);
+}
+template <typename Char, typename OutputIt>
+OutputIt copy_unit(string_view unit, OutputIt out, Char) {
+  return std::copy(unit.begin(), unit.end(), out);
+}
+
+template <typename OutputIt>
+OutputIt copy_unit(string_view unit, OutputIt out, wchar_t) {
+  // This works when wchar_t is UTF-32 because units only contain characters
+  // that have the same representation in UTF-16 and UTF-32.
+  utf8_to_utf16 u(unit);
+  return std::copy(u.c_str(), u.c_str() + u.size(), out);
+}
+
+template <typename Char, typename Period, typename OutputIt>
+OutputIt format_duration_unit(OutputIt out) {
+  if (const char* unit = get_units<Period>())
+    return copy_unit(string_view(unit), out, Char());
+  const Char num_f[] = {'[', '{', '}', ']', 's', 0};
+  if (const_check(Period::den == 1)) return format_to(out, num_f, Period::num);
+  const Char num_def_f[] = {'[', '{', '}', '/', '{', '}', ']', 's', 0};
+  return format_to(out, num_def_f, Period::num, Period::den);
+}
+
+template <typename FormatContext, typename OutputIt, typename Rep,
+          typename Period>
+struct chrono_formatter {
+  FormatContext& context;
+  OutputIt out;
+  int precision;
+  // rep is unsigned to avoid overflow.
+  using rep =
+      conditional_t<std::is_integral<Rep>::value && sizeof(Rep) < sizeof(int),
+                    unsigned, typename make_unsigned_or_unchanged<Rep>::type>;
+  rep val;
+  using seconds = std::chrono::duration<rep>;
+  seconds s;
+  using milliseconds = std::chrono::duration<rep, std::milli>;
+  bool negative;
+
+  using char_type = typename FormatContext::char_type;
+
+  explicit chrono_formatter(FormatContext& ctx, OutputIt o,
+                            std::chrono::duration<Rep, Period> d)
+      : context(ctx),
+        out(o),
+        val(static_cast<rep>(d.count())),
+        negative(false) {
+    if (d.count() < 0) {
+      val = 0 - val;
+      negative = true;
+    }
+
+    // this may overflow and/or the result may not fit in the
+    // target type.
+#if FMT_SAFE_DURATION_CAST
+    // might need checked conversion (rep!=Rep)
+    auto tmpval = std::chrono::duration<rep, Period>(val);
+    s = fmt_safe_duration_cast<seconds>(tmpval);
+#else
+    s = std::chrono::duration_cast<seconds>(
+        std::chrono::duration<rep, Period>(val));
+#endif
+  }
+
+  // returns true if nan or inf, writes to out.
+  bool handle_nan_inf() {
+    if (isfinite(val)) {
+      return false;
+    }
+    if (isnan(val)) {
+      write_nan();
+      return true;
+    }
+    // must be +-inf
+    if (val > 0) {
+      write_pinf();
+    } else {
+      write_ninf();
+    }
+    return true;
+  }
+
+  Rep hour() const { return static_cast<Rep>(mod((s.count() / 3600), 24)); }
+
+  Rep hour12() const {
+    Rep hour = static_cast<Rep>(mod((s.count() / 3600), 12));
+    return hour <= 0 ? 12 : hour;
+  }
+
+  Rep minute() const { return static_cast<Rep>(mod((s.count() / 60), 60)); }
+  Rep second() const { return static_cast<Rep>(mod(s.count(), 60)); }
+
+  std::tm time() const {
+    auto time = std::tm();
+    time.tm_hour = to_nonnegative_int(hour(), 24);
+    time.tm_min = to_nonnegative_int(minute(), 60);
+    time.tm_sec = to_nonnegative_int(second(), 60);
+    return time;
+  }
+
+  void write_sign() {
+    if (negative) {
+      *out++ = '-';
+      negative = false;
+    }
+  }
+
+  void write(Rep value, int width) {
+    write_sign();
+    if (isnan(value)) return write_nan();
+    uint32_or_64_or_128_t<int> n =
+        to_unsigned(to_nonnegative_int(value, max_value<int>()));
+    int num_digits = detail::count_digits(n);
+    if (width > num_digits) out = std::fill_n(out, width - num_digits, '0');
+    out = format_decimal<char_type>(out, n, num_digits).end;
+  }
+
+  void write_nan() { std::copy_n("nan", 3, out); }
+  void write_pinf() { std::copy_n("inf", 3, out); }
+  void write_ninf() { std::copy_n("-inf", 4, out); }
+
+  void format_localized(const tm& time, char format, char modifier = 0) {
+    if (isnan(val)) return write_nan();
+    auto locale = context.locale().template get<std::locale>();
+    auto& facet = std::use_facet<std::time_put<char_type>>(locale);
+    std::basic_ostringstream<char_type> os;
+    os.imbue(locale);
+    facet.put(os, os, ' ', &time, format, modifier);
+    auto str = os.str();
+    std::copy(str.begin(), str.end(), out);
+  }
+
+  void on_text(const char_type* begin, const char_type* end) {
+    std::copy(begin, end, out);
+  }
+
+  // These are not implemented because durations don't have date information.
+  void on_abbr_weekday() {}
+  void on_full_weekday() {}
+  void on_dec0_weekday(numeric_system) {}
+  void on_dec1_weekday(numeric_system) {}
+  void on_abbr_month() {}
+  void on_full_month() {}
+  void on_datetime(numeric_system) {}
+  void on_loc_date(numeric_system) {}
+  void on_loc_time(numeric_system) {}
+  void on_us_date() {}
+  void on_iso_date() {}
+  void on_utc_offset() {}
+  void on_tz_name() {}
+
+  void on_24_hour(numeric_system ns) {
+    if (handle_nan_inf()) return;
+
+    if (ns == numeric_system::standard) return write(hour(), 2);
+    auto time = tm();
+    time.tm_hour = to_nonnegative_int(hour(), 24);
+    format_localized(time, 'H', 'O');
+  }
+
+  void on_12_hour(numeric_system ns) {
+    if (handle_nan_inf()) return;
+
+    if (ns == numeric_system::standard) return write(hour12(), 2);
+    auto time = tm();
+    time.tm_hour = to_nonnegative_int(hour12(), 12);
+    format_localized(time, 'I', 'O');
+  }
+
+  void on_minute(numeric_system ns) {
+    if (handle_nan_inf()) return;
+
+    if (ns == numeric_system::standard) return write(minute(), 2);
+    auto time = tm();
+    time.tm_min = to_nonnegative_int(minute(), 60);
+    format_localized(time, 'M', 'O');
+  }
+
+  void on_second(numeric_system ns) {
+    if (handle_nan_inf()) return;
+
+    if (ns == numeric_system::standard) {
+      write(second(), 2);
+#if FMT_SAFE_DURATION_CAST
+      // convert rep->Rep
+      using duration_rep = std::chrono::duration<rep, Period>;
+      using duration_Rep = std::chrono::duration<Rep, Period>;
+      auto tmpval = fmt_safe_duration_cast<duration_Rep>(duration_rep{val});
+#else
+      auto tmpval = std::chrono::duration<Rep, Period>(val);
+#endif
+      auto ms = get_milliseconds(tmpval);
+      if (ms != std::chrono::milliseconds(0)) {
+        *out++ = '.';
+        write(ms.count(), 3);
+      }
+      return;
+    }
+    auto time = tm();
+    time.tm_sec = to_nonnegative_int(second(), 60);
+    format_localized(time, 'S', 'O');
+  }
+
+  void on_12_hour_time() {
+    if (handle_nan_inf()) return;
+    format_localized(time(), 'r');
+  }
+
+  void on_24_hour_time() {
+    if (handle_nan_inf()) {
+      *out++ = ':';
+      handle_nan_inf();
+      return;
+    }
+
+    write(hour(), 2);
+    *out++ = ':';
+    write(minute(), 2);
+  }
+
+  void on_iso_time() {
+    on_24_hour_time();
+    *out++ = ':';
+    if (handle_nan_inf()) return;
+    write(second(), 2);
+  }
+
+  void on_am_pm() {
+    if (handle_nan_inf()) return;
+    format_localized(time(), 'p');
+  }
+
+  void on_duration_value() {
+    if (handle_nan_inf()) return;
+    write_sign();
+    out = format_duration_value<char_type>(out, val, precision);
+  }
+
+  void on_duration_unit() {
+    out = format_duration_unit<char_type, Period>(out);
+  }
+};
+}  // namespace detail
+
+template <typename Rep, typename Period, typename Char>
+struct formatter<std::chrono::duration<Rep, Period>, Char> {
+ private:
+  basic_format_specs<Char> specs;
+  int precision;
+  using arg_ref_type = detail::arg_ref<Char>;
+  arg_ref_type width_ref;
+  arg_ref_type precision_ref;
+  mutable basic_string_view<Char> format_str;
+  using duration = std::chrono::duration<Rep, Period>;
+
+  struct spec_handler {
+    formatter& f;
+    basic_format_parse_context<Char>& context;
+    basic_string_view<Char> format_str;
+
+    template <typename Id> FMT_CONSTEXPR arg_ref_type make_arg_ref(Id arg_id) {
+      context.check_arg_id(arg_id);
+      return arg_ref_type(arg_id);
+    }
+
+    FMT_CONSTEXPR arg_ref_type make_arg_ref(basic_string_view<Char> arg_id) {
+      context.check_arg_id(arg_id);
+      return arg_ref_type(arg_id);
+    }
+
+    FMT_CONSTEXPR arg_ref_type make_arg_ref(detail::auto_id) {
+      return arg_ref_type(context.next_arg_id());
+    }
+
+    void on_error(const char* msg) { FMT_THROW(format_error(msg)); }
+    void on_fill(basic_string_view<Char> fill) { f.specs.fill = fill; }
+    void on_align(align_t align) { f.specs.align = align; }
+    void on_width(int width) { f.specs.width = width; }
+    void on_precision(int _precision) { f.precision = _precision; }
+    void end_precision() {}
+
+    template <typename Id> void on_dynamic_width(Id arg_id) {
+      f.width_ref = make_arg_ref(arg_id);
+    }
+
+    template <typename Id> void on_dynamic_precision(Id arg_id) {
+      f.precision_ref = make_arg_ref(arg_id);
+    }
+  };
+
+  using iterator = typename basic_format_parse_context<Char>::iterator;
+  struct parse_range {
+    iterator begin;
+    iterator end;
+  };
+
+  FMT_CONSTEXPR parse_range do_parse(basic_format_parse_context<Char>& ctx) {
+    auto begin = ctx.begin(), end = ctx.end();
+    if (begin == end || *begin == '}') return {begin, begin};
+    spec_handler handler{*this, ctx, format_str};
+    begin = detail::parse_align(begin, end, handler);
+    if (begin == end) return {begin, begin};
+    begin = detail::parse_width(begin, end, handler);
+    if (begin == end) return {begin, begin};
+    if (*begin == '.') {
+      if (std::is_floating_point<Rep>::value)
+        begin = detail::parse_precision(begin, end, handler);
+      else
+        handler.on_error("precision not allowed for this argument type");
+    }
+    end = parse_chrono_format(begin, end, detail::chrono_format_checker());
+    return {begin, end};
+  }
+
+ public:
+  formatter() : precision(-1) {}
+
+  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
+      -> decltype(ctx.begin()) {
+    auto range = do_parse(ctx);
+    format_str = basic_string_view<Char>(
+        &*range.begin, detail::to_unsigned(range.end - range.begin));
+    return range.end;
+  }
+
+  template <typename FormatContext>
+  auto format(const duration& d, FormatContext& ctx) -> decltype(ctx.out()) {
+    auto begin = format_str.begin(), end = format_str.end();
+    // As a possible future optimization, we could avoid extra copying if width
+    // is not specified.
+    basic_memory_buffer<Char> buf;
+    auto out = std::back_inserter(buf);
+    detail::handle_dynamic_spec<detail::width_checker>(specs.width, width_ref,
+                                                       ctx);
+    detail::handle_dynamic_spec<detail::precision_checker>(precision,
+                                                           precision_ref, ctx);
+    if (begin == end || *begin == '}') {
+      out = detail::format_duration_value<Char>(out, d.count(), precision);
+      detail::format_duration_unit<Char, Period>(out);
+    } else {
+      detail::chrono_formatter<FormatContext, decltype(out), Rep, Period> f(
+          ctx, out, d);
+      f.precision = precision;
+      parse_chrono_format(begin, end, f);
+    }
+    return detail::write(
+        ctx.out(), basic_string_view<Char>(buf.data(), buf.size()), specs);
+  }
+};
+
+FMT_END_NAMESPACE
+
+#endif  // FMT_CHRONO_H_
diff --git a/external/fmtlib/include/fmt/color.h b/external/fmtlib/include/fmt/color.h
new file mode 100644
index 000000000..b65f892af
--- /dev/null
+++ b/external/fmtlib/include/fmt/color.h
@@ -0,0 +1,566 @@
+// Formatting library for C++ - color support
+//
+// Copyright (c) 2018 - present, Victor Zverovich and fmt contributors
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+#ifndef FMT_COLOR_H_
+#define FMT_COLOR_H_
+
+#include "format.h"
+
+FMT_BEGIN_NAMESPACE
+
+enum class color : uint32_t {
+  alice_blue = 0xF0F8FF,               // rgb(240,248,255)
+  antique_white = 0xFAEBD7,            // rgb(250,235,215)
+  aqua = 0x00FFFF,                     // rgb(0,255,255)
+  aquamarine = 0x7FFFD4,               // rgb(127,255,212)
+  azure = 0xF0FFFF,                    // rgb(240,255,255)
+  beige = 0xF5F5DC,                    // rgb(245,245,220)
+  bisque = 0xFFE4C4,                   // rgb(255,228,196)
+  black = 0x000000,                    // rgb(0,0,0)
+  blanched_almond = 0xFFEBCD,          // rgb(255,235,205)
+  blue = 0x0000FF,                     // rgb(0,0,255)
+  blue_violet = 0x8A2BE2,              // rgb(138,43,226)
+  brown = 0xA52A2A,                    // rgb(165,42,42)
+  burly_wood = 0xDEB887,               // rgb(222,184,135)
+  cadet_blue = 0x5F9EA0,               // rgb(95,158,160)
+  chartreuse = 0x7FFF00,               // rgb(127,255,0)
+  chocolate = 0xD2691E,                // rgb(210,105,30)
+  coral = 0xFF7F50,                    // rgb(255,127,80)
+  cornflower_blue = 0x6495ED,          // rgb(100,149,237)
+  cornsilk = 0xFFF8DC,                 // rgb(255,248,220)
+  crimson = 0xDC143C,                  // rgb(220,20,60)
+  cyan = 0x00FFFF,                     // rgb(0,255,255)
+  dark_blue = 0x00008B,                // rgb(0,0,139)
+  dark_cyan = 0x008B8B,                // rgb(0,139,139)
+  dark_golden_rod = 0xB8860B,          // rgb(184,134,11)
+  dark_gray = 0xA9A9A9,                // rgb(169,169,169)
+  dark_green = 0x006400,               // rgb(0,100,0)
+  dark_khaki = 0xBDB76B,               // rgb(189,183,107)
+  dark_magenta = 0x8B008B,             // rgb(139,0,139)
+  dark_olive_green = 0x556B2F,         // rgb(85,107,47)
+  dark_orange = 0xFF8C00,              // rgb(255,140,0)
+  dark_orchid = 0x9932CC,              // rgb(153,50,204)
+  dark_red = 0x8B0000,                 // rgb(139,0,0)
+  dark_salmon = 0xE9967A,              // rgb(233,150,122)
+  dark_sea_green = 0x8FBC8F,           // rgb(143,188,143)
+  dark_slate_blue = 0x483D8B,          // rgb(72,61,139)
+  dark_slate_gray = 0x2F4F4F,          // rgb(47,79,79)
+  dark_turquoise = 0x00CED1,           // rgb(0,206,209)
+  dark_violet = 0x9400D3,              // rgb(148,0,211)
+  deep_pink = 0xFF1493,                // rgb(255,20,147)
+  deep_sky_blue = 0x00BFFF,            // rgb(0,191,255)
+  dim_gray = 0x696969,                 // rgb(105,105,105)
+  dodger_blue = 0x1E90FF,              // rgb(30,144,255)
+  fire_brick = 0xB22222,               // rgb(178,34,34)
+  floral_white = 0xFFFAF0,             // rgb(255,250,240)
+  forest_green = 0x228B22,             // rgb(34,139,34)
+  fuchsia = 0xFF00FF,                  // rgb(255,0,255)
+  gainsboro = 0xDCDCDC,                // rgb(220,220,220)
+  ghost_white = 0xF8F8FF,              // rgb(248,248,255)
+  gold = 0xFFD700,                     // rgb(255,215,0)
+  golden_rod = 0xDAA520,               // rgb(218,165,32)
+  gray = 0x808080,                     // rgb(128,128,128)
+  green = 0x008000,                    // rgb(0,128,0)
+  green_yellow = 0xADFF2F,             // rgb(173,255,47)
+  honey_dew = 0xF0FFF0,                // rgb(240,255,240)
+  hot_pink = 0xFF69B4,                 // rgb(255,105,180)
+  indian_red = 0xCD5C5C,               // rgb(205,92,92)
+  indigo = 0x4B0082,                   // rgb(75,0,130)
+  ivory = 0xFFFFF0,                    // rgb(255,255,240)
+  khaki = 0xF0E68C,                    // rgb(240,230,140)
+  lavender = 0xE6E6FA,                 // rgb(230,230,250)
+  lavender_blush = 0xFFF0F5,           // rgb(255,240,245)
+  lawn_green = 0x7CFC00,               // rgb(124,252,0)
+  lemon_chiffon = 0xFFFACD,            // rgb(255,250,205)
+  light_blue = 0xADD8E6,               // rgb(173,216,230)
+  light_coral = 0xF08080,              // rgb(240,128,128)
+  light_cyan = 0xE0FFFF,               // rgb(224,255,255)
+  light_golden_rod_yellow = 0xFAFAD2,  // rgb(250,250,210)
+  light_gray = 0xD3D3D3,               // rgb(211,211,211)
+  light_green = 0x90EE90,              // rgb(144,238,144)
+  light_pink = 0xFFB6C1,               // rgb(255,182,193)
+  light_salmon = 0xFFA07A,             // rgb(255,160,122)
+  light_sea_green = 0x20B2AA,          // rgb(32,178,170)
+  light_sky_blue = 0x87CEFA,           // rgb(135,206,250)
+  light_slate_gray = 0x778899,         // rgb(119,136,153)
+  light_steel_blue = 0xB0C4DE,         // rgb(176,196,222)
+  light_yellow = 0xFFFFE0,             // rgb(255,255,224)
+  lime = 0x00FF00,                     // rgb(0,255,0)
+  lime_green = 0x32CD32,               // rgb(50,205,50)
+  linen = 0xFAF0E6,                    // rgb(250,240,230)
+  magenta = 0xFF00FF,                  // rgb(255,0,255)
+  maroon = 0x800000,                   // rgb(128,0,0)
+  medium_aquamarine = 0x66CDAA,        // rgb(102,205,170)
+  medium_blue = 0x0000CD,              // rgb(0,0,205)
+  medium_orchid = 0xBA55D3,            // rgb(186,85,211)
+  medium_purple = 0x9370DB,            // rgb(147,112,219)
+  medium_sea_green = 0x3CB371,         // rgb(60,179,113)
+  medium_slate_blue = 0x7B68EE,        // rgb(123,104,238)
+  medium_spring_green = 0x00FA9A,      // rgb(0,250,154)
+  medium_turquoise = 0x48D1CC,         // rgb(72,209,204)
+  medium_violet_red = 0xC71585,        // rgb(199,21,133)
+  midnight_blue = 0x191970,            // rgb(25,25,112)
+  mint_cream = 0xF5FFFA,               // rgb(245,255,250)
+  misty_rose = 0xFFE4E1,               // rgb(255,228,225)
+  moccasin = 0xFFE4B5,                 // rgb(255,228,181)
+  navajo_white = 0xFFDEAD,             // rgb(255,222,173)
+  navy = 0x000080,                     // rgb(0,0,128)
+  old_lace = 0xFDF5E6,                 // rgb(253,245,230)
+  olive = 0x808000,                    // rgb(128,128,0)
+  olive_drab = 0x6B8E23,               // rgb(107,142,35)
+  orange = 0xFFA500,                   // rgb(255,165,0)
+  orange_red = 0xFF4500,               // rgb(255,69,0)
+  orchid = 0xDA70D6,                   // rgb(218,112,214)
+  pale_golden_rod = 0xEEE8AA,          // rgb(238,232,170)
+  pale_green = 0x98FB98,               // rgb(152,251,152)
+  pale_turquoise = 0xAFEEEE,           // rgb(175,238,238)
+  pale_violet_red = 0xDB7093,          // rgb(219,112,147)
+  papaya_whip = 0xFFEFD5,              // rgb(255,239,213)
+  peach_puff = 0xFFDAB9,               // rgb(255,218,185)
+  peru = 0xCD853F,                     // rgb(205,133,63)
+  pink = 0xFFC0CB,                     // rgb(255,192,203)
+  plum = 0xDDA0DD,                     // rgb(221,160,221)
+  powder_blue = 0xB0E0E6,              // rgb(176,224,230)
+  purple = 0x800080,                   // rgb(128,0,128)
+  rebecca_purple = 0x663399,           // rgb(102,51,153)
+  red = 0xFF0000,                      // rgb(255,0,0)
+  rosy_brown = 0xBC8F8F,               // rgb(188,143,143)
+  royal_blue = 0x4169E1,               // rgb(65,105,225)
+  saddle_brown = 0x8B4513,             // rgb(139,69,19)
+  salmon = 0xFA8072,                   // rgb(250,128,114)
+  sandy_brown = 0xF4A460,              // rgb(244,164,96)
+  sea_green = 0x2E8B57,                // rgb(46,139,87)
+  sea_shell = 0xFFF5EE,                // rgb(255,245,238)
+  sienna = 0xA0522D,                   // rgb(160,82,45)
+  silver = 0xC0C0C0,                   // rgb(192,192,192)
+  sky_blue = 0x87CEEB,                 // rgb(135,206,235)
+  slate_blue = 0x6A5ACD,               // rgb(106,90,205)
+  slate_gray = 0x708090,               // rgb(112,128,144)
+  snow = 0xFFFAFA,                     // rgb(255,250,250)
+  spring_green = 0x00FF7F,             // rgb(0,255,127)
+  steel_blue = 0x4682B4,               // rgb(70,130,180)
+  tan = 0xD2B48C,                      // rgb(210,180,140)
+  teal = 0x008080,                     // rgb(0,128,128)
+  thistle = 0xD8BFD8,                  // rgb(216,191,216)
+  tomato = 0xFF6347,                   // rgb(255,99,71)
+  turquoise = 0x40E0D0,                // rgb(64,224,208)
+  violet = 0xEE82EE,                   // rgb(238,130,238)
+  wheat = 0xF5DEB3,                    // rgb(245,222,179)
+  white = 0xFFFFFF,                    // rgb(255,255,255)
+  white_smoke = 0xF5F5F5,              // rgb(245,245,245)
+  yellow = 0xFFFF00,                   // rgb(255,255,0)
+  yellow_green = 0x9ACD32              // rgb(154,205,50)
+};                                     // enum class color
+
+enum class terminal_color : uint8_t {
+  black = 30,
+  red,
+  green,
+  yellow,
+  blue,
+  magenta,
+  cyan,
+  white,
+  bright_black = 90,
+  bright_red,
+  bright_green,
+  bright_yellow,
+  bright_blue,
+  bright_magenta,
+  bright_cyan,
+  bright_white
+};
+
+enum class emphasis : uint8_t {
+  bold = 1,
+  italic = 1 << 1,
+  underline = 1 << 2,
+  strikethrough = 1 << 3
+};
+
+// rgb is a struct for red, green and blue colors.
+// Using the name "rgb" makes some editors show the color in a tooltip.
+struct rgb {
+  FMT_CONSTEXPR rgb() : r(0), g(0), b(0) {}
+  FMT_CONSTEXPR rgb(uint8_t r_, uint8_t g_, uint8_t b_) : r(r_), g(g_), b(b_) {}
+  FMT_CONSTEXPR rgb(uint32_t hex)
+      : r((hex >> 16) & 0xFF), g((hex >> 8) & 0xFF), b(hex & 0xFF) {}
+  FMT_CONSTEXPR rgb(color hex)
+      : r((uint32_t(hex) >> 16) & 0xFF),
+        g((uint32_t(hex) >> 8) & 0xFF),
+        b(uint32_t(hex) & 0xFF) {}
+  uint8_t r;
+  uint8_t g;
+  uint8_t b;
+};
+
+namespace detail {
+
+// color is a struct of either a rgb color or a terminal color.
+struct color_type {
+  FMT_CONSTEXPR color_type() FMT_NOEXCEPT : is_rgb(), value{} {}
+  FMT_CONSTEXPR color_type(color rgb_color) FMT_NOEXCEPT : is_rgb(true),
+                                                           value{} {
+    value.rgb_color = static_cast<uint32_t>(rgb_color);
+  }
+  FMT_CONSTEXPR color_type(rgb rgb_color) FMT_NOEXCEPT : is_rgb(true), value{} {
+    value.rgb_color = (static_cast<uint32_t>(rgb_color.r) << 16) |
+                      (static_cast<uint32_t>(rgb_color.g) << 8) | rgb_color.b;
+  }
+  FMT_CONSTEXPR color_type(terminal_color term_color) FMT_NOEXCEPT : is_rgb(),
+                                                                     value{} {
+    value.term_color = static_cast<uint8_t>(term_color);
+  }
+  bool is_rgb;
+  union color_union {
+    uint8_t term_color;
+    uint32_t rgb_color;
+  } value;
+};
+}  // namespace detail
+
+// Experimental text formatting support.
+class text_style {
+ public:
+  FMT_CONSTEXPR text_style(emphasis em = emphasis()) FMT_NOEXCEPT
+      : set_foreground_color(),
+        set_background_color(),
+        ems(em) {}
+
+  FMT_CONSTEXPR text_style& operator|=(const text_style& rhs) {
+    if (!set_foreground_color) {
+      set_foreground_color = rhs.set_foreground_color;
+      foreground_color = rhs.foreground_color;
+    } else if (rhs.set_foreground_color) {
+      if (!foreground_color.is_rgb || !rhs.foreground_color.is_rgb)
+        FMT_THROW(format_error("can't OR a terminal color"));
+      foreground_color.value.rgb_color |= rhs.foreground_color.value.rgb_color;
+    }
+
+    if (!set_background_color) {
+      set_background_color = rhs.set_background_color;
+      background_color = rhs.background_color;
+    } else if (rhs.set_background_color) {
+      if (!background_color.is_rgb || !rhs.background_color.is_rgb)
+        FMT_THROW(format_error("can't OR a terminal color"));
+      background_color.value.rgb_color |= rhs.background_color.value.rgb_color;
+    }
+
+    ems = static_cast<emphasis>(static_cast<uint8_t>(ems) |
+                                static_cast<uint8_t>(rhs.ems));
+    return *this;
+  }
+
+  friend FMT_CONSTEXPR text_style operator|(text_style lhs,
+                                            const text_style& rhs) {
+    return lhs |= rhs;
+  }
+
+  FMT_CONSTEXPR text_style& operator&=(const text_style& rhs) {
+    if (!set_foreground_color) {
+      set_foreground_color = rhs.set_foreground_color;
+      foreground_color = rhs.foreground_color;
+    } else if (rhs.set_foreground_color) {
+      if (!foreground_color.is_rgb || !rhs.foreground_color.is_rgb)
+        FMT_THROW(format_error("can't AND a terminal color"));
+      foreground_color.value.rgb_color &= rhs.foreground_color.value.rgb_color;
+    }
+
+    if (!set_background_color) {
+      set_background_color = rhs.set_background_color;
+      background_color = rhs.background_color;
+    } else if (rhs.set_background_color) {
+      if (!background_color.is_rgb || !rhs.background_color.is_rgb)
+        FMT_THROW(format_error("can't AND a terminal color"));
+      background_color.value.rgb_color &= rhs.background_color.value.rgb_color;
+    }
+
+    ems = static_cast<emphasis>(static_cast<uint8_t>(ems) &
+                                static_cast<uint8_t>(rhs.ems));
+    return *this;
+  }
+
+  friend FMT_CONSTEXPR text_style operator&(text_style lhs,
+                                            const text_style& rhs) {
+    return lhs &= rhs;
+  }
+
+  FMT_CONSTEXPR bool has_foreground() const FMT_NOEXCEPT {
+    return set_foreground_color;
+  }
+  FMT_CONSTEXPR bool has_background() const FMT_NOEXCEPT {
+    return set_background_color;
+  }
+  FMT_CONSTEXPR bool has_emphasis() const FMT_NOEXCEPT {
+    return static_cast<uint8_t>(ems) != 0;
+  }
+  FMT_CONSTEXPR detail::color_type get_foreground() const FMT_NOEXCEPT {
+    FMT_ASSERT(has_foreground(), "no foreground specified for this style");
+    return foreground_color;
+  }
+  FMT_CONSTEXPR detail::color_type get_background() const FMT_NOEXCEPT {
+    FMT_ASSERT(has_background(), "no background specified for this style");
+    return background_color;
+  }
+  FMT_CONSTEXPR emphasis get_emphasis() const FMT_NOEXCEPT {
+    FMT_ASSERT(has_emphasis(), "no emphasis specified for this style");
+    return ems;
+  }
+
+ private:
+  FMT_CONSTEXPR text_style(bool is_foreground,
+                           detail::color_type text_color) FMT_NOEXCEPT
+      : set_foreground_color(),
+        set_background_color(),
+        ems() {
+    if (is_foreground) {
+      foreground_color = text_color;
+      set_foreground_color = true;
+    } else {
+      background_color = text_color;
+      set_background_color = true;
+    }
+  }
+
+  friend FMT_CONSTEXPR_DECL text_style fg(detail::color_type foreground)
+      FMT_NOEXCEPT;
+  friend FMT_CONSTEXPR_DECL text_style bg(detail::color_type background)
+      FMT_NOEXCEPT;
+
+  detail::color_type foreground_color;
+  detail::color_type background_color;
+  bool set_foreground_color;
+  bool set_background_color;
+  emphasis ems;
+};
+
+FMT_CONSTEXPR text_style fg(detail::color_type foreground) FMT_NOEXCEPT {
+  return text_style(/*is_foreground=*/true, foreground);
+}
+
+FMT_CONSTEXPR text_style bg(detail::color_type background) FMT_NOEXCEPT {
+  return text_style(/*is_foreground=*/false, background);
+}
+
+FMT_CONSTEXPR text_style operator|(emphasis lhs, emphasis rhs) FMT_NOEXCEPT {
+  return text_style(lhs) | rhs;
+}
+
+namespace detail {
+
+template <typename Char> struct ansi_color_escape {
+  FMT_CONSTEXPR ansi_color_escape(detail::color_type text_color,
+                                  const char* esc) FMT_NOEXCEPT {
+    // If we have a terminal color, we need to output another escape code
+    // sequence.
+    if (!text_color.is_rgb) {
+      bool is_background = esc == detail::data::background_color;
+      uint32_t value = text_color.value.term_color;
+      // Background ASCII codes are the same as the foreground ones but with
+      // 10 more.
+      if (is_background) value += 10u;
+
+      size_t index = 0;
+      buffer[index++] = static_cast<Char>('\x1b');
+      buffer[index++] = static_cast<Char>('[');
+
+      if (value >= 100u) {
+        buffer[index++] = static_cast<Char>('1');
+        value %= 100u;
+      }
+      buffer[index++] = static_cast<Char>('0' + value / 10u);
+      buffer[index++] = static_cast<Char>('0' + value % 10u);
+
+      buffer[index++] = static_cast<Char>('m');
+      buffer[index++] = static_cast<Char>('\0');
+      return;
+    }
+
+    for (int i = 0; i < 7; i++) {
+      buffer[i] = static_cast<Char>(esc[i]);
+    }
+    rgb color(text_color.value.rgb_color);
+    to_esc(color.r, buffer + 7, ';');
+    to_esc(color.g, buffer + 11, ';');
+    to_esc(color.b, buffer + 15, 'm');
+    buffer[19] = static_cast<Char>(0);
+  }
+  FMT_CONSTEXPR ansi_color_escape(emphasis em) FMT_NOEXCEPT {
+    uint8_t em_codes[4] = {};
+    uint8_t em_bits = static_cast<uint8_t>(em);
+    if (em_bits & static_cast<uint8_t>(emphasis::bold)) em_codes[0] = 1;
+    if (em_bits & static_cast<uint8_t>(emphasis::italic)) em_codes[1] = 3;
+    if (em_bits & static_cast<uint8_t>(emphasis::underline)) em_codes[2] = 4;
+    if (em_bits & static_cast<uint8_t>(emphasis::strikethrough))
+      em_codes[3] = 9;
+
+    size_t index = 0;
+    for (int i = 0; i < 4; ++i) {
+      if (!em_codes[i]) continue;
+      buffer[index++] = static_cast<Char>('\x1b');
+      buffer[index++] = static_cast<Char>('[');
+      buffer[index++] = static_cast<Char>('0' + em_codes[i]);
+      buffer[index++] = static_cast<Char>('m');
+    }
+    buffer[index++] = static_cast<Char>(0);
+  }
+  FMT_CONSTEXPR operator const Char*() const FMT_NOEXCEPT { return buffer; }
+
+  FMT_CONSTEXPR const Char* begin() const FMT_NOEXCEPT { return buffer; }
+  FMT_CONSTEXPR const Char* end() const FMT_NOEXCEPT {
+    return buffer + std::char_traits<Char>::length(buffer);
+  }
+
+ private:
+  Char buffer[7u + 3u * 4u + 1u];
+
+  static FMT_CONSTEXPR void to_esc(uint8_t c, Char* out,
+                                   char delimiter) FMT_NOEXCEPT {
+    out[0] = static_cast<Char>('0' + c / 100);
+    out[1] = static_cast<Char>('0' + c / 10 % 10);
+    out[2] = static_cast<Char>('0' + c % 10);
+    out[3] = static_cast<Char>(delimiter);
+  }
+};
+
+template <typename Char>
+FMT_CONSTEXPR ansi_color_escape<Char> make_foreground_color(
+    detail::color_type foreground) FMT_NOEXCEPT {
+  return ansi_color_escape<Char>(foreground, detail::data::foreground_color);
+}
+
+template <typename Char>
+FMT_CONSTEXPR ansi_color_escape<Char> make_background_color(
+    detail::color_type background) FMT_NOEXCEPT {
+  return ansi_color_escape<Char>(background, detail::data::background_color);
+}
+
+template <typename Char>
+FMT_CONSTEXPR ansi_color_escape<Char> make_emphasis(emphasis em) FMT_NOEXCEPT {
+  return ansi_color_escape<Char>(em);
+}
+
+template <typename Char>
+inline void fputs(const Char* chars, FILE* stream) FMT_NOEXCEPT {
+  std::fputs(chars, stream);
+}
+
+template <>
+inline void fputs<wchar_t>(const wchar_t* chars, FILE* stream) FMT_NOEXCEPT {
+  std::fputws(chars, stream);
+}
+
+template <typename Char> inline void reset_color(FILE* stream) FMT_NOEXCEPT {
+  fputs(detail::data::reset_color, stream);
+}
+
+template <> inline void reset_color<wchar_t>(FILE* stream) FMT_NOEXCEPT {
+  fputs(detail::data::wreset_color, stream);
+}
+
+template <typename Char>
+inline void reset_color(basic_memory_buffer<Char>& buffer) FMT_NOEXCEPT {
+  const char* begin = data::reset_color;
+  const char* end = begin + sizeof(data::reset_color) - 1;
+  buffer.append(begin, end);
+}
+
+template <typename Char>
+void vformat_to(basic_memory_buffer<Char>& buf, const text_style& ts,
+                basic_string_view<Char> format_str,
+                basic_format_args<buffer_context<Char>> args) {
+  bool has_style = false;
+  if (ts.has_emphasis()) {
+    has_style = true;
+    auto emphasis = detail::make_emphasis<Char>(ts.get_emphasis());
+    buf.append(emphasis.begin(), emphasis.end());
+  }
+  if (ts.has_foreground()) {
+    has_style = true;
+    auto foreground = detail::make_foreground_color<Char>(ts.get_foreground());
+    buf.append(foreground.begin(), foreground.end());
+  }
+  if (ts.has_background()) {
+    has_style = true;
+    auto background = detail::make_background_color<Char>(ts.get_background());
+    buf.append(background.begin(), background.end());
+  }
+  detail::vformat_to(buf, format_str, args);
+  if (has_style) detail::reset_color<Char>(buf);
+}
+}  // namespace detail
+
+template <typename S, typename Char = char_t<S>>
+void vprint(std::FILE* f, const text_style& ts, const S& format,
+            basic_format_args<buffer_context<Char>> args) {
+  basic_memory_buffer<Char> buf;
+  detail::vformat_to(buf, ts, to_string_view(format), args);
+  buf.push_back(Char(0));
+  detail::fputs(buf.data(), f);
+}
+
+/**
+  Formats a string and prints it to the specified file stream using ANSI
+  escape sequences to specify text formatting.
+  Example:
+    fmt::print(fmt::emphasis::bold | fg(fmt::color::red),
+               "Elapsed time: {0:.2f} seconds", 1.23);
+ */
+template <typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_string<S>::value)>
+void print(std::FILE* f, const text_style& ts, const S& format_str,
+           const Args&... args) {
+  detail::check_format_string<Args...>(format_str);
+  using context = buffer_context<char_t<S>>;
+  format_arg_store<context, Args...> as{args...};
+  vprint(f, ts, format_str, basic_format_args<context>(as));
+}
+
+/**
+  Formats a string and prints it to stdout using ANSI escape sequences to
+  specify text formatting.
+  Example:
+    fmt::print(fmt::emphasis::bold | fg(fmt::color::red),
+               "Elapsed time: {0:.2f} seconds", 1.23);
+ */
+template <typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_string<S>::value)>
+void print(const text_style& ts, const S& format_str, const Args&... args) {
+  return print(stdout, ts, format_str, args...);
+}
+
+template <typename S, typename Char = char_t<S>>
+inline std::basic_string<Char> vformat(
+    const text_style& ts, const S& format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+  basic_memory_buffer<Char> buf;
+  detail::vformat_to(buf, ts, to_string_view(format_str), args);
+  return fmt::to_string(buf);
+}
+
+/**
+  \rst
+  Formats arguments and returns the result as a string using ANSI
+  escape sequences to specify text formatting.
+
+  **Example**::
+
+    #include <fmt/color.h>
+    std::string message = fmt::format(fmt::emphasis::bold | fg(fmt::color::red),
+                                      "The answer is {}", 42);
+  \endrst
+*/
+template <typename S, typename... Args, typename Char = char_t<S>>
+inline std::basic_string<Char> format(const text_style& ts, const S& format_str,
+                                      const Args&... args) {
+  return vformat(ts, to_string_view(format_str),
+                 detail::make_args_checked<Args...>(format_str, args...));
+}
+
+FMT_END_NAMESPACE
+
+#endif  // FMT_COLOR_H_
diff --git a/external/fmtlib/include/fmt/compile.h b/external/fmtlib/include/fmt/compile.h
new file mode 100644
index 000000000..d7e6449eb
--- /dev/null
+++ b/external/fmtlib/include/fmt/compile.h
@@ -0,0 +1,665 @@
+// Formatting library for C++ - experimental format string compilation
+//
+// Copyright (c) 2012 - present, Victor Zverovich and fmt contributors
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+#ifndef FMT_COMPILE_H_
+#define FMT_COMPILE_H_
+
+#include <vector>
+
+#include "format.h"
+
+FMT_BEGIN_NAMESPACE
+namespace detail {
+
+// A compile-time string which is compiled into fast formatting code.
+class compiled_string {};
+
+template <typename S>
+struct is_compiled_string : std::is_base_of<compiled_string, S> {};
+
+/**
+  \rst
+  Converts a string literal *s* into a format string that will be parsed at
+  compile time and converted into efficient formatting code. Requires C++17
+  ``constexpr if`` compiler support.
+
+  **Example**::
+
+    // Converts 42 into std::string using the most efficient method and no
+    // runtime format string processing.
+    std::string s = fmt::format(FMT_COMPILE("{}"), 42);
+  \endrst
+ */
+#define FMT_COMPILE(s) FMT_STRING_IMPL(s, fmt::detail::compiled_string)
+
+template <typename T, typename... Tail>
+const T& first(const T& value, const Tail&...) {
+  return value;
+}
+
+// Part of a compiled format string. It can be either literal text or a
+// replacement field.
+template <typename Char> struct format_part {
+  enum class kind { arg_index, arg_name, text, replacement };
+
+  struct replacement {
+    arg_ref<Char> arg_id;
+    dynamic_format_specs<Char> specs;
+  };
+
+  kind part_kind;
+  union value {
+    int arg_index;
+    basic_string_view<Char> str;
+    replacement repl;
+
+    FMT_CONSTEXPR value(int index = 0) : arg_index(index) {}
+    FMT_CONSTEXPR value(basic_string_view<Char> s) : str(s) {}
+    FMT_CONSTEXPR value(replacement r) : repl(r) {}
+  } val;
+  // Position past the end of the argument id.
+  const Char* arg_id_end = nullptr;
+
+  FMT_CONSTEXPR format_part(kind k = kind::arg_index, value v = {})
+      : part_kind(k), val(v) {}
+
+  static FMT_CONSTEXPR format_part make_arg_index(int index) {
+    return format_part(kind::arg_index, index);
+  }
+  static FMT_CONSTEXPR format_part make_arg_name(basic_string_view<Char> name) {
+    return format_part(kind::arg_name, name);
+  }
+  static FMT_CONSTEXPR format_part make_text(basic_string_view<Char> text) {
+    return format_part(kind::text, text);
+  }
+  static FMT_CONSTEXPR format_part make_replacement(replacement repl) {
+    return format_part(kind::replacement, repl);
+  }
+};
+
+template <typename Char> struct part_counter {
+  unsigned num_parts = 0;
+
+  FMT_CONSTEXPR void on_text(const Char* begin, const Char* end) {
+    if (begin != end) ++num_parts;
+  }
+
+  FMT_CONSTEXPR int on_arg_id() { return ++num_parts, 0; }
+  FMT_CONSTEXPR int on_arg_id(int) { return ++num_parts, 0; }
+  FMT_CONSTEXPR int on_arg_id(basic_string_view<Char>) {
+    return ++num_parts, 0;
+  }
+
+  FMT_CONSTEXPR void on_replacement_field(int, const Char*) {}
+
+  FMT_CONSTEXPR const Char* on_format_specs(int, const Char* begin,
+                                            const Char* end) {
+    // Find the matching brace.
+    unsigned brace_counter = 0;
+    for (; begin != end; ++begin) {
+      if (*begin == '{') {
+        ++brace_counter;
+      } else if (*begin == '}') {
+        if (brace_counter == 0u) break;
+        --brace_counter;
+      }
+    }
+    return begin;
+  }
+
+  FMT_CONSTEXPR void on_error(const char*) {}
+};
+
+// Counts the number of parts in a format string.
+template <typename Char>
+FMT_CONSTEXPR unsigned count_parts(basic_string_view<Char> format_str) {
+  part_counter<Char> counter;
+  parse_format_string<true>(format_str, counter);
+  return counter.num_parts;
+}
+
+template <typename Char, typename PartHandler>
+class format_string_compiler : public error_handler {
+ private:
+  using part = format_part<Char>;
+
+  PartHandler handler_;
+  part part_;
+  basic_string_view<Char> format_str_;
+  basic_format_parse_context<Char> parse_context_;
+
+ public:
+  FMT_CONSTEXPR format_string_compiler(basic_string_view<Char> format_str,
+                                       PartHandler handler)
+      : handler_(handler),
+        format_str_(format_str),
+        parse_context_(format_str) {}
+
+  FMT_CONSTEXPR void on_text(const Char* begin, const Char* end) {
+    if (begin != end)
+      handler_(part::make_text({begin, to_unsigned(end - begin)}));
+  }
+
+  FMT_CONSTEXPR int on_arg_id() {
+    part_ = part::make_arg_index(parse_context_.next_arg_id());
+    return 0;
+  }
+
+  FMT_CONSTEXPR int on_arg_id(int id) {
+    parse_context_.check_arg_id(id);
+    part_ = part::make_arg_index(id);
+    return 0;
+  }
+
+  FMT_CONSTEXPR int on_arg_id(basic_string_view<Char> id) {
+    part_ = part::make_arg_name(id);
+    return 0;
+  }
+
+  FMT_CONSTEXPR void on_replacement_field(int, const Char* ptr) {
+    part_.arg_id_end = ptr;
+    handler_(part_);
+  }
+
+  FMT_CONSTEXPR const Char* on_format_specs(int, const Char* begin,
+                                            const Char* end) {
+    auto repl = typename part::replacement();
+    dynamic_specs_handler<basic_format_parse_context<Char>> handler(
+        repl.specs, parse_context_);
+    auto it = parse_format_specs(begin, end, handler);
+    if (*it != '}') on_error("missing '}' in format string");
+    repl.arg_id = part_.part_kind == part::kind::arg_index
+                      ? arg_ref<Char>(part_.val.arg_index)
+                      : arg_ref<Char>(part_.val.str);
+    auto part = part::make_replacement(repl);
+    part.arg_id_end = begin;
+    handler_(part);
+    return it;
+  }
+};
+
+// Compiles a format string and invokes handler(part) for each parsed part.
+template <bool IS_CONSTEXPR, typename Char, typename PartHandler>
+FMT_CONSTEXPR void compile_format_string(basic_string_view<Char> format_str,
+                                         PartHandler handler) {
+  parse_format_string<IS_CONSTEXPR>(
+      format_str,
+      format_string_compiler<Char, PartHandler>(format_str, handler));
+}
+
+template <typename OutputIt, typename Context, typename Id>
+void format_arg(
+    basic_format_parse_context<typename Context::char_type>& parse_ctx,
+    Context& ctx, Id arg_id) {
+  ctx.advance_to(visit_format_arg(
+      arg_formatter<OutputIt, typename Context::char_type>(ctx, &parse_ctx),
+      ctx.arg(arg_id)));
+}
+
+// vformat_to is defined in a subnamespace to prevent ADL.
+namespace cf {
+template <typename Context, typename OutputIt, typename CompiledFormat>
+auto vformat_to(OutputIt out, CompiledFormat& cf,
+                basic_format_args<Context> args) -> typename Context::iterator {
+  using char_type = typename Context::char_type;
+  basic_format_parse_context<char_type> parse_ctx(
+      to_string_view(cf.format_str_));
+  Context ctx(out, args);
+
+  const auto& parts = cf.parts();
+  for (auto part_it = std::begin(parts); part_it != std::end(parts);
+       ++part_it) {
+    const auto& part = *part_it;
+    const auto& value = part.val;
+
+    using format_part_t = format_part<char_type>;
+    switch (part.part_kind) {
+    case format_part_t::kind::text: {
+      const auto text = value.str;
+      auto output = ctx.out();
+      auto&& it = reserve(output, text.size());
+      it = std::copy_n(text.begin(), text.size(), it);
+      ctx.advance_to(output);
+      break;
+    }
+
+    case format_part_t::kind::arg_index:
+      advance_to(parse_ctx, part.arg_id_end);
+      detail::format_arg<OutputIt>(parse_ctx, ctx, value.arg_index);
+      break;
+
+    case format_part_t::kind::arg_name:
+      advance_to(parse_ctx, part.arg_id_end);
+      detail::format_arg<OutputIt>(parse_ctx, ctx, value.str);
+      break;
+
+    case format_part_t::kind::replacement: {
+      const auto& arg_id_value = value.repl.arg_id.val;
+      const auto arg = value.repl.arg_id.kind == arg_id_kind::index
+                           ? ctx.arg(arg_id_value.index)
+                           : ctx.arg(arg_id_value.name);
+
+      auto specs = value.repl.specs;
+
+      handle_dynamic_spec<width_checker>(specs.width, specs.width_ref, ctx);
+      handle_dynamic_spec<precision_checker>(specs.precision,
+                                             specs.precision_ref, ctx);
+
+      error_handler h;
+      numeric_specs_checker<error_handler> checker(h, arg.type());
+      if (specs.align == align::numeric) checker.require_numeric_argument();
+      if (specs.sign != sign::none) checker.check_sign();
+      if (specs.alt) checker.require_numeric_argument();
+      if (specs.precision >= 0) checker.check_precision();
+
+      advance_to(parse_ctx, part.arg_id_end);
+      ctx.advance_to(
+          visit_format_arg(arg_formatter<OutputIt, typename Context::char_type>(
+                               ctx, nullptr, &specs),
+                           arg));
+      break;
+    }
+    }
+  }
+  return ctx.out();
+}
+}  // namespace cf
+
+struct basic_compiled_format {};
+
+template <typename S, typename = void>
+struct compiled_format_base : basic_compiled_format {
+  using char_type = char_t<S>;
+  using parts_container = std::vector<detail::format_part<char_type>>;
+
+  parts_container compiled_parts;
+
+  explicit compiled_format_base(basic_string_view<char_type> format_str) {
+    compile_format_string<false>(format_str,
+                                 [this](const format_part<char_type>& part) {
+                                   compiled_parts.push_back(part);
+                                 });
+  }
+
+  const parts_container& parts() const { return compiled_parts; }
+};
+
+template <typename Char, unsigned N> struct format_part_array {
+  format_part<Char> data[N] = {};
+  FMT_CONSTEXPR format_part_array() = default;
+};
+
+template <typename Char, unsigned N>
+FMT_CONSTEXPR format_part_array<Char, N> compile_to_parts(
+    basic_string_view<Char> format_str) {
+  format_part_array<Char, N> parts;
+  unsigned counter = 0;
+  // This is not a lambda for compatibility with older compilers.
+  struct {
+    format_part<Char>* parts;
+    unsigned* counter;
+    FMT_CONSTEXPR void operator()(const format_part<Char>& part) {
+      parts[(*counter)++] = part;
+    }
+  } collector{parts.data, &counter};
+  compile_format_string<true>(format_str, collector);
+  if (counter < N) {
+    parts.data[counter] =
+        format_part<Char>::make_text(basic_string_view<Char>());
+  }
+  return parts;
+}
+
+template <typename T> constexpr const T& constexpr_max(const T& a, const T& b) {
+  return (a < b) ? b : a;
+}
+
+template <typename S>
+struct compiled_format_base<S, enable_if_t<is_compile_string<S>::value>>
+    : basic_compiled_format {
+  using char_type = char_t<S>;
+
+  FMT_CONSTEXPR explicit compiled_format_base(basic_string_view<char_type>) {}
+
+// Workaround for old compilers. Format string compilation will not be
+// performed there anyway.
+#if FMT_USE_CONSTEXPR
+  static FMT_CONSTEXPR_DECL const unsigned num_format_parts =
+      constexpr_max(count_parts(to_string_view(S())), 1u);
+#else
+  static const unsigned num_format_parts = 1;
+#endif
+
+  using parts_container = format_part<char_type>[num_format_parts];
+
+  const parts_container& parts() const {
+    static FMT_CONSTEXPR_DECL const auto compiled_parts =
+        compile_to_parts<char_type, num_format_parts>(
+            detail::to_string_view(S()));
+    return compiled_parts.data;
+  }
+};
+
+template <typename S, typename... Args>
+class compiled_format : private compiled_format_base<S> {
+ public:
+  using typename compiled_format_base<S>::char_type;
+
+ private:
+  basic_string_view<char_type> format_str_;
+
+  template <typename Context, typename OutputIt, typename CompiledFormat>
+  friend auto cf::vformat_to(OutputIt out, CompiledFormat& cf,
+                             basic_format_args<Context> args) ->
+      typename Context::iterator;
+
+ public:
+  compiled_format() = delete;
+  explicit constexpr compiled_format(basic_string_view<char_type> format_str)
+      : compiled_format_base<S>(format_str), format_str_(format_str) {}
+};
+
+#ifdef __cpp_if_constexpr
+template <typename... Args> struct type_list {};
+
+// Returns a reference to the argument at index N from [first, rest...].
+template <int N, typename T, typename... Args>
+constexpr const auto& get(const T& first, const Args&... rest) {
+  static_assert(N < 1 + sizeof...(Args), "index is out of bounds");
+  if constexpr (N == 0)
+    return first;
+  else
+    return get<N - 1>(rest...);
+}
+
+template <int N, typename> struct get_type_impl;
+
+template <int N, typename... Args> struct get_type_impl<N, type_list<Args...>> {
+  using type = remove_cvref_t<decltype(get<N>(std::declval<Args>()...))>;
+};
+
+template <int N, typename T>
+using get_type = typename get_type_impl<N, T>::type;
+
+template <typename T> struct is_compiled_format : std::false_type {};
+
+template <typename Char> struct text {
+  basic_string_view<Char> data;
+  using char_type = Char;
+
+  template <typename OutputIt, typename... Args>
+  OutputIt format(OutputIt out, const Args&...) const {
+    return write<Char>(out, data);
+  }
+};
+
+template <typename Char>
+struct is_compiled_format<text<Char>> : std::true_type {};
+
+template <typename Char>
+constexpr text<Char> make_text(basic_string_view<Char> s, size_t pos,
+                               size_t size) {
+  return {{&s[pos], size}};
+}
+
+// A replacement field that refers to argument N.
+template <typename Char, typename T, int N> struct field {
+  using char_type = Char;
+
+  template <typename OutputIt, typename... Args>
+  OutputIt format(OutputIt out, const Args&... args) const {
+    // This ensures that the argument type is convertile to `const T&`.
+    const T& arg = get<N>(args...);
+    return write<Char>(out, arg);
+  }
+};
+
+template <typename Char, typename T, int N>
+struct is_compiled_format<field<Char, T, N>> : std::true_type {};
+
+// A replacement field that refers to argument N and has format specifiers.
+template <typename Char, typename T, int N> struct spec_field {
+  using char_type = Char;
+  mutable formatter<T, Char> fmt;
+
+  template <typename OutputIt, typename... Args>
+  OutputIt format(OutputIt out, const Args&... args) const {
+    // This ensures that the argument type is convertile to `const T&`.
+    const T& arg = get<N>(args...);
+    basic_format_context<OutputIt, Char> ctx(out, {});
+    return fmt.format(arg, ctx);
+  }
+};
+
+template <typename Char, typename T, int N>
+struct is_compiled_format<spec_field<Char, T, N>> : std::true_type {};
+
+template <typename L, typename R> struct concat {
+  L lhs;
+  R rhs;
+  using char_type = typename L::char_type;
+
+  template <typename OutputIt, typename... Args>
+  OutputIt format(OutputIt out, const Args&... args) const {
+    out = lhs.format(out, args...);
+    return rhs.format(out, args...);
+  }
+};
+
+template <typename L, typename R>
+struct is_compiled_format<concat<L, R>> : std::true_type {};
+
+template <typename L, typename R>
+constexpr concat<L, R> make_concat(L lhs, R rhs) {
+  return {lhs, rhs};
+}
+
+struct unknown_format {};
+
+template <typename Char>
+constexpr size_t parse_text(basic_string_view<Char> str, size_t pos) {
+  for (size_t size = str.size(); pos != size; ++pos) {
+    if (str[pos] == '{' || str[pos] == '}') break;
+  }
+  return pos;
+}
+
+template <typename Args, size_t POS, int ID, typename S>
+constexpr auto compile_format_string(S format_str);
+
+template <typename Args, size_t POS, int ID, typename T, typename S>
+constexpr auto parse_tail(T head, S format_str) {
+  if constexpr (POS !=
+                basic_string_view<typename S::char_type>(format_str).size()) {
+    constexpr auto tail = compile_format_string<Args, POS, ID>(format_str);
+    if constexpr (std::is_same<remove_cvref_t<decltype(tail)>,
+                               unknown_format>())
+      return tail;
+    else
+      return make_concat(head, tail);
+  } else {
+    return head;
+  }
+}
+
+template <typename T, typename Char> struct parse_specs_result {
+  formatter<T, Char> fmt;
+  size_t end;
+};
+
+template <typename T, typename Char>
+constexpr parse_specs_result<T, Char> parse_specs(basic_string_view<Char> str,
+                                                  size_t pos) {
+  str.remove_prefix(pos);
+  auto ctx = basic_format_parse_context<Char>(str);
+  auto f = formatter<T, Char>();
+  auto end = f.parse(ctx);
+  return {f, pos + (end - str.data()) + 1};
+}
+
+// Compiles a non-empty format string and returns the compiled representation
+// or unknown_format() on unrecognized input.
+template <typename Args, size_t POS, int ID, typename S>
+constexpr auto compile_format_string(S format_str) {
+  using char_type = typename S::char_type;
+  constexpr basic_string_view<char_type> str = format_str;
+  if constexpr (str[POS] == '{') {
+    if (POS + 1 == str.size())
+      throw format_error("unmatched '{' in format string");
+    if constexpr (str[POS + 1] == '{') {
+      return parse_tail<Args, POS + 2, ID>(make_text(str, POS, 1), format_str);
+    } else if constexpr (str[POS + 1] == '}') {
+      using type = get_type<ID, Args>;
+      return parse_tail<Args, POS + 2, ID + 1>(field<char_type, type, ID>(),
+                                               format_str);
+    } else if constexpr (str[POS + 1] == ':') {
+      using type = get_type<ID, Args>;
+      constexpr auto result = parse_specs<type>(str, POS + 2);
+      return parse_tail<Args, result.end, ID + 1>(
+          spec_field<char_type, type, ID>{result.fmt}, format_str);
+    } else {
+      return unknown_format();
+    }
+  } else if constexpr (str[POS] == '}') {
+    if (POS + 1 == str.size())
+      throw format_error("unmatched '}' in format string");
+    return parse_tail<Args, POS + 2, ID>(make_text(str, POS, 1), format_str);
+  } else {
+    constexpr auto end = parse_text(str, POS + 1);
+    return parse_tail<Args, end, ID>(make_text(str, POS, end - POS),
+                                     format_str);
+  }
+}
+
+template <typename... Args, typename S,
+          FMT_ENABLE_IF(is_compile_string<S>::value ||
+                        detail::is_compiled_string<S>::value)>
+constexpr auto compile(S format_str) {
+  constexpr basic_string_view<typename S::char_type> str = format_str;
+  if constexpr (str.size() == 0) {
+    return detail::make_text(str, 0, 0);
+  } else {
+    constexpr auto result =
+        detail::compile_format_string<detail::type_list<Args...>, 0, 0>(
+            format_str);
+    if constexpr (std::is_same<remove_cvref_t<decltype(result)>,
+                               detail::unknown_format>()) {
+      return detail::compiled_format<S, Args...>(to_string_view(format_str));
+    } else {
+      return result;
+    }
+  }
+}
+#else
+template <typename... Args, typename S,
+          FMT_ENABLE_IF(is_compile_string<S>::value)>
+constexpr auto compile(S format_str) -> detail::compiled_format<S, Args...> {
+  return detail::compiled_format<S, Args...>(to_string_view(format_str));
+}
+#endif  // __cpp_if_constexpr
+
+// Compiles the format string which must be a string literal.
+template <typename... Args, typename Char, size_t N>
+auto compile(const Char (&format_str)[N])
+    -> detail::compiled_format<const Char*, Args...> {
+  return detail::compiled_format<const Char*, Args...>(
+      basic_string_view<Char>(format_str, N - 1));
+}
+}  // namespace detail
+
+// DEPRECATED! use FMT_COMPILE instead.
+template <typename... Args>
+FMT_DEPRECATED auto compile(const Args&... args)
+    -> decltype(detail::compile(args...)) {
+  return detail::compile(args...);
+}
+
+#if FMT_USE_CONSTEXPR
+#  ifdef __cpp_if_constexpr
+
+template <typename CompiledFormat, typename... Args,
+          typename Char = typename CompiledFormat::char_type,
+          FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
+FMT_INLINE std::basic_string<Char> format(const CompiledFormat& cf,
+                                          const Args&... args) {
+  basic_memory_buffer<Char> buffer;
+  detail::buffer<Char>& base = buffer;
+  cf.format(std::back_inserter(base), args...);
+  return to_string(buffer);
+}
+
+template <typename OutputIt, typename CompiledFormat, typename... Args,
+          FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
+OutputIt format_to(OutputIt out, const CompiledFormat& cf,
+                   const Args&... args) {
+  return cf.format(out, args...);
+}
+#  endif  // __cpp_if_constexpr
+#endif    // FMT_USE_CONSTEXPR
+
+template <typename CompiledFormat, typename... Args,
+          typename Char = typename CompiledFormat::char_type,
+          FMT_ENABLE_IF(std::is_base_of<detail::basic_compiled_format,
+                                        CompiledFormat>::value)>
+std::basic_string<Char> format(const CompiledFormat& cf, const Args&... args) {
+  basic_memory_buffer<Char> buffer;
+  using context = buffer_context<Char>;
+  detail::buffer<Char>& base = buffer;
+  detail::cf::vformat_to<context>(std::back_inserter(base), cf,
+                                  make_format_args<context>(args...));
+  return to_string(buffer);
+}
+
+template <typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+FMT_INLINE std::basic_string<typename S::char_type> format(const S&,
+                                                           Args&&... args) {
+  constexpr basic_string_view<typename S::char_type> str = S();
+  if (str.size() == 2 && str[0] == '{' && str[1] == '}')
+    return fmt::to_string(detail::first(args...));
+  constexpr auto compiled = detail::compile<Args...>(S());
+  return format(compiled, std::forward<Args>(args)...);
+}
+
+template <typename OutputIt, typename CompiledFormat, typename... Args,
+          FMT_ENABLE_IF(std::is_base_of<detail::basic_compiled_format,
+                                        CompiledFormat>::value)>
+OutputIt format_to(OutputIt out, const CompiledFormat& cf,
+                   const Args&... args) {
+  using char_type = typename CompiledFormat::char_type;
+  using context = format_context_t<OutputIt, char_type>;
+  return detail::cf::vformat_to<context>(out, cf,
+                                         make_format_args<context>(args...));
+}
+
+template <typename OutputIt, typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+OutputIt format_to(OutputIt out, const S&, const Args&... args) {
+  constexpr auto compiled = detail::compile<Args...>(S());
+  return format_to(out, compiled, args...);
+}
+
+template <
+    typename OutputIt, typename CompiledFormat, typename... Args,
+    FMT_ENABLE_IF(detail::is_output_iterator<OutputIt>::value&& std::is_base_of<
+                  detail::basic_compiled_format, CompiledFormat>::value)>
+format_to_n_result<OutputIt> format_to_n(OutputIt out, size_t n,
+                                         const CompiledFormat& cf,
+                                         const Args&... args) {
+  auto it =
+      format_to(detail::truncating_iterator<OutputIt>(out, n), cf, args...);
+  return {it.base(), it.count()};
+}
+
+template <typename CompiledFormat, typename... Args>
+size_t formatted_size(const CompiledFormat& cf, const Args&... args) {
+  return format_to(detail::counting_iterator(), cf, args...).count();
+}
+
+FMT_END_NAMESPACE
+
+#endif  // FMT_COMPILE_H_
diff --git a/external/fmtlib/include/fmt/core.h b/external/fmtlib/include/fmt/core.h
new file mode 100644
index 000000000..37799a3a0
--- /dev/null
+++ b/external/fmtlib/include/fmt/core.h
@@ -0,0 +1,1882 @@
+// Formatting library for C++ - the core API
+//
+// Copyright (c) 2012 - present, Victor Zverovich
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+#ifndef FMT_CORE_H_
+#define FMT_CORE_H_
+
+#include <cstdio>  // std::FILE
+#include <cstring>
+#include <functional>
+#include <iterator>
+#include <memory>
+#include <string>
+#include <type_traits>
+#include <vector>
+
+// The fmt library version in the form major * 10000 + minor * 100 + patch.
+#define FMT_VERSION 70003
+
+#ifdef __clang__
+#  define FMT_CLANG_VERSION (__clang_major__ * 100 + __clang_minor__)
+#else
+#  define FMT_CLANG_VERSION 0
+#endif
+
+#if defined(__GNUC__) && !defined(__clang__)
+#  define FMT_GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
+#else
+#  define FMT_GCC_VERSION 0
+#endif
+
+#if defined(__INTEL_COMPILER)
+#  define FMT_ICC_VERSION __INTEL_COMPILER
+#else
+#  define FMT_ICC_VERSION 0
+#endif
+
+#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
+#  define FMT_HAS_GXX_CXX11 FMT_GCC_VERSION
+#else
+#  define FMT_HAS_GXX_CXX11 0
+#endif
+
+#ifdef __NVCC__
+#  define FMT_NVCC __NVCC__
+#else
+#  define FMT_NVCC 0
+#endif
+
+#ifdef _MSC_VER
+#  define FMT_MSC_VER _MSC_VER
+#  define FMT_SUPPRESS_MSC_WARNING(n) __pragma(warning(suppress : n))
+#else
+#  define FMT_MSC_VER 0
+#  define FMT_SUPPRESS_MSC_WARNING(n)
+#endif
+#ifdef __has_feature
+#  define FMT_HAS_FEATURE(x) __has_feature(x)
+#else
+#  define FMT_HAS_FEATURE(x) 0
+#endif
+
+#if defined(__has_include) && !defined(__INTELLISENSE__) && \
+    !(FMT_ICC_VERSION && FMT_ICC_VERSION < 1600)
+#  define FMT_HAS_INCLUDE(x) __has_include(x)
+#else
+#  define FMT_HAS_INCLUDE(x) 0
+#endif
+
+#ifdef __has_cpp_attribute
+#  define FMT_HAS_CPP_ATTRIBUTE(x) __has_cpp_attribute(x)
+#else
+#  define FMT_HAS_CPP_ATTRIBUTE(x) 0
+#endif
+
+#define FMT_HAS_CPP14_ATTRIBUTE(attribute) \
+  (__cplusplus >= 201402L && FMT_HAS_CPP_ATTRIBUTE(attribute))
+
+#define FMT_HAS_CPP17_ATTRIBUTE(attribute) \
+  (__cplusplus >= 201703L && FMT_HAS_CPP_ATTRIBUTE(attribute))
+
+// Check if relaxed C++14 constexpr is supported.
+// GCC doesn't allow throw in constexpr until version 6 (bug 67371).
+#ifndef FMT_USE_CONSTEXPR
+#  define FMT_USE_CONSTEXPR                                           \
+    (FMT_HAS_FEATURE(cxx_relaxed_constexpr) || FMT_MSC_VER >= 1910 || \
+     (FMT_GCC_VERSION >= 600 && __cplusplus >= 201402L)) &&           \
+        !FMT_NVCC && !FMT_ICC_VERSION
+#endif
+#if FMT_USE_CONSTEXPR
+#  define FMT_CONSTEXPR constexpr
+#  define FMT_CONSTEXPR_DECL constexpr
+#else
+#  define FMT_CONSTEXPR inline
+#  define FMT_CONSTEXPR_DECL
+#endif
+
+#ifndef FMT_OVERRIDE
+#  if FMT_HAS_FEATURE(cxx_override) || \
+      (FMT_GCC_VERSION >= 408 && FMT_HAS_GXX_CXX11) || FMT_MSC_VER >= 1900
+#    define FMT_OVERRIDE override
+#  else
+#    define FMT_OVERRIDE
+#  endif
+#endif
+
+// Check if exceptions are disabled.
+#ifndef FMT_EXCEPTIONS
+#  if (defined(__GNUC__) && !defined(__EXCEPTIONS)) || \
+      FMT_MSC_VER && !_HAS_EXCEPTIONS
+#    define FMT_EXCEPTIONS 0
+#  else
+#    define FMT_EXCEPTIONS 1
+#  endif
+#endif
+
+// Define FMT_USE_NOEXCEPT to make fmt use noexcept (C++11 feature).
+#ifndef FMT_USE_NOEXCEPT
+#  define FMT_USE_NOEXCEPT 0
+#endif
+
+#if FMT_USE_NOEXCEPT || FMT_HAS_FEATURE(cxx_noexcept) || \
+    (FMT_GCC_VERSION >= 408 && FMT_HAS_GXX_CXX11) || FMT_MSC_VER >= 1900
+#  define FMT_DETECTED_NOEXCEPT noexcept
+#  define FMT_HAS_CXX11_NOEXCEPT 1
+#else
+#  define FMT_DETECTED_NOEXCEPT throw()
+#  define FMT_HAS_CXX11_NOEXCEPT 0
+#endif
+
+#ifndef FMT_NOEXCEPT
+#  if FMT_EXCEPTIONS || FMT_HAS_CXX11_NOEXCEPT
+#    define FMT_NOEXCEPT FMT_DETECTED_NOEXCEPT
+#  else
+#    define FMT_NOEXCEPT
+#  endif
+#endif
+
+// [[noreturn]] is disabled on MSVC and NVCC because of bogus unreachable code
+// warnings.
+#if FMT_EXCEPTIONS && FMT_HAS_CPP_ATTRIBUTE(noreturn) && !FMT_MSC_VER && \
+    !FMT_NVCC
+#  define FMT_NORETURN [[noreturn]]
+#else
+#  define FMT_NORETURN
+#endif
+
+#ifndef FMT_DEPRECATED
+#  if FMT_HAS_CPP14_ATTRIBUTE(deprecated) || FMT_MSC_VER >= 1900
+#    define FMT_DEPRECATED [[deprecated]]
+#  else
+#    if defined(__GNUC__) || defined(__clang__)
+#      define FMT_DEPRECATED __attribute__((deprecated))
+#    elif FMT_MSC_VER
+#      define FMT_DEPRECATED __declspec(deprecated)
+#    else
+#      define FMT_DEPRECATED /* deprecated */
+#    endif
+#  endif
+#endif
+
+// Workaround broken [[deprecated]] in the Intel, PGI and NVCC compilers.
+#if FMT_ICC_VERSION || defined(__PGI) || FMT_NVCC
+#  define FMT_DEPRECATED_ALIAS
+#else
+#  define FMT_DEPRECATED_ALIAS FMT_DEPRECATED
+#endif
+
+#ifndef FMT_INLINE
+#  if FMT_GCC_VERSION || FMT_CLANG_VERSION
+#    define FMT_INLINE inline __attribute__((always_inline))
+#  else
+#    define FMT_INLINE inline
+#  endif
+#endif
+
+#ifndef FMT_BEGIN_NAMESPACE
+#  if FMT_HAS_FEATURE(cxx_inline_namespaces) || FMT_GCC_VERSION >= 404 || \
+      FMT_MSC_VER >= 1900
+#    define FMT_INLINE_NAMESPACE inline namespace
+#    define FMT_END_NAMESPACE \
+      }                       \
+      }
+#  else
+#    define FMT_INLINE_NAMESPACE namespace
+#    define FMT_END_NAMESPACE \
+      }                       \
+      using namespace v7;     \
+      }
+#  endif
+#  define FMT_BEGIN_NAMESPACE \
+    namespace fmt {           \
+    FMT_INLINE_NAMESPACE v7 {
+#endif
+
+#if !defined(FMT_HEADER_ONLY) && defined(_WIN32)
+#  define FMT_CLASS_API FMT_SUPPRESS_MSC_WARNING(4275)
+#  ifdef FMT_EXPORT
+#    define FMT_API __declspec(dllexport)
+#    define FMT_EXTERN_TEMPLATE_API FMT_API
+#    define FMT_EXPORTED
+#  elif defined(FMT_SHARED)
+#    define FMT_API __declspec(dllimport)
+#    define FMT_EXTERN_TEMPLATE_API FMT_API
+#  endif
+#else
+#  define FMT_CLASS_API
+#endif
+#ifndef FMT_API
+#  define FMT_API
+#endif
+#ifndef FMT_EXTERN_TEMPLATE_API
+#  define FMT_EXTERN_TEMPLATE_API
+#endif
+#ifndef FMT_INSTANTIATION_DEF_API
+#  define FMT_INSTANTIATION_DEF_API FMT_API
+#endif
+
+#ifndef FMT_HEADER_ONLY
+#  define FMT_EXTERN extern
+#else
+#  define FMT_EXTERN
+#endif
+
+// libc++ supports string_view in pre-c++17.
+#if (FMT_HAS_INCLUDE(<string_view>) &&                       \
+     (__cplusplus > 201402L || defined(_LIBCPP_VERSION))) || \
+    (defined(_MSVC_LANG) && _MSVC_LANG > 201402L && _MSC_VER >= 1910)
+#  include <string_view>
+#  define FMT_USE_STRING_VIEW
+#elif FMT_HAS_INCLUDE("experimental/string_view") && __cplusplus >= 201402L
+#  include <experimental/string_view>
+#  define FMT_USE_EXPERIMENTAL_STRING_VIEW
+#endif
+
+#ifndef FMT_UNICODE
+#  define FMT_UNICODE !FMT_MSC_VER
+#endif
+#if FMT_UNICODE && FMT_MSC_VER
+#  pragma execution_character_set("utf-8")
+#endif
+
+FMT_BEGIN_NAMESPACE
+
+// Implementations of enable_if_t and other metafunctions for older systems.
+template <bool B, class T = void>
+using enable_if_t = typename std::enable_if<B, T>::type;
+template <bool B, class T, class F>
+using conditional_t = typename std::conditional<B, T, F>::type;
+template <bool B> using bool_constant = std::integral_constant<bool, B>;
+template <typename T>
+using remove_reference_t = typename std::remove_reference<T>::type;
+template <typename T>
+using remove_const_t = typename std::remove_const<T>::type;
+template <typename T>
+using remove_cvref_t = typename std::remove_cv<remove_reference_t<T>>::type;
+template <typename T> struct type_identity { using type = T; };
+template <typename T> using type_identity_t = typename type_identity<T>::type;
+
+struct monostate {};
+
+// An enable_if helper to be used in template parameters which results in much
+// shorter symbols: https://godbolt.org/z/sWw4vP. Extra parentheses are needed
+// to workaround a bug in MSVC 2019 (see #1140 and #1186).
+#define FMT_ENABLE_IF(...) enable_if_t<(__VA_ARGS__), int> = 0
+
+namespace detail {
+
+// A helper function to suppress bogus "conditional expression is constant"
+// warnings.
+template <typename T> constexpr T const_check(T value) { return value; }
+
+FMT_NORETURN FMT_API void assert_fail(const char* file, int line,
+                                      const char* message);
+
+#ifndef FMT_ASSERT
+#  ifdef NDEBUG
+// FMT_ASSERT is not empty to avoid -Werror=empty-body.
+#    define FMT_ASSERT(condition, message) ((void)0)
+#  else
+#    define FMT_ASSERT(condition, message)                                    \
+      ((condition) /* void() fails with -Winvalid-constexpr on clang 4.0.1 */ \
+           ? (void)0                                                          \
+           : ::fmt::detail::assert_fail(__FILE__, __LINE__, (message)))
+#  endif
+#endif
+
+#if defined(FMT_USE_STRING_VIEW)
+template <typename Char> using std_string_view = std::basic_string_view<Char>;
+#elif defined(FMT_USE_EXPERIMENTAL_STRING_VIEW)
+template <typename Char>
+using std_string_view = std::experimental::basic_string_view<Char>;
+#else
+template <typename T> struct std_string_view {};
+#endif
+
+#ifdef FMT_USE_INT128
+// Do nothing.
+#elif defined(__SIZEOF_INT128__) && !FMT_NVCC && !(FMT_CLANG_VERSION && FMT_MSC_VER)
+#  define FMT_USE_INT128 1
+using int128_t = __int128_t;
+using uint128_t = __uint128_t;
+#else
+#  define FMT_USE_INT128 0
+#endif
+#if !FMT_USE_INT128
+struct int128_t {};
+struct uint128_t {};
+#endif
+
+// Casts a nonnegative integer to unsigned.
+template <typename Int>
+FMT_CONSTEXPR typename std::make_unsigned<Int>::type to_unsigned(Int value) {
+  FMT_ASSERT(value >= 0, "negative value");
+  return static_cast<typename std::make_unsigned<Int>::type>(value);
+}
+
+FMT_SUPPRESS_MSC_WARNING(4566) constexpr unsigned char micro[] = "\u00B5";
+
+template <typename Char> constexpr bool is_unicode() {
+  return FMT_UNICODE || sizeof(Char) != 1 ||
+         (sizeof(micro) == 3 && micro[0] == 0xC2 && micro[1] == 0xB5);
+}
+
+#ifdef __cpp_char8_t
+using char8_type = char8_t;
+#else
+enum char8_type : unsigned char {};
+#endif
+}  // namespace detail
+
+#ifdef FMT_USE_INTERNAL
+namespace internal = detail;  // DEPRECATED
+#endif
+
+/**
+  An implementation of ``std::basic_string_view`` for pre-C++17. It provides a
+  subset of the API. ``fmt::basic_string_view`` is used for format strings even
+  if ``std::string_view`` is available to prevent issues when a library is
+  compiled with a different ``-std`` option than the client code (which is not
+  recommended).
+ */
+template <typename Char> class basic_string_view {
+ private:
+  const Char* data_;
+  size_t size_;
+
+ public:
+  using value_type = Char;
+  using iterator = const Char*;
+
+  constexpr basic_string_view() FMT_NOEXCEPT : data_(nullptr), size_(0) {}
+
+  /** Constructs a string reference object from a C string and a size. */
+  constexpr basic_string_view(const Char* s, size_t count) FMT_NOEXCEPT
+      : data_(s),
+        size_(count) {}
+
+  /**
+    \rst
+    Constructs a string reference object from a C string computing
+    the size with ``std::char_traits<Char>::length``.
+    \endrst
+   */
+#if __cplusplus >= 201703L  // C++17's char_traits::length() is constexpr.
+  FMT_CONSTEXPR
+#endif
+  basic_string_view(const Char* s)
+      : data_(s), size_(std::char_traits<Char>::length(s)) {}
+
+  /** Constructs a string reference from a ``std::basic_string`` object. */
+  template <typename Traits, typename Alloc>
+  FMT_CONSTEXPR basic_string_view(
+      const std::basic_string<Char, Traits, Alloc>& s) FMT_NOEXCEPT
+      : data_(s.data()),
+        size_(s.size()) {}
+
+  template <typename S, FMT_ENABLE_IF(std::is_same<
+                                      S, detail::std_string_view<Char>>::value)>
+  FMT_CONSTEXPR basic_string_view(S s) FMT_NOEXCEPT : data_(s.data()),
+                                                      size_(s.size()) {}
+
+  /** Returns a pointer to the string data. */
+  constexpr const Char* data() const { return data_; }
+
+  /** Returns the string size. */
+  constexpr size_t size() const { return size_; }
+
+  constexpr iterator begin() const { return data_; }
+  constexpr iterator end() const { return data_ + size_; }
+
+  constexpr const Char& operator[](size_t pos) const { return data_[pos]; }
+
+  FMT_CONSTEXPR void remove_prefix(size_t n) {
+    data_ += n;
+    size_ -= n;
+  }
+
+  // Lexicographically compare this string reference to other.
+  int compare(basic_string_view other) const {
+    size_t str_size = size_ < other.size_ ? size_ : other.size_;
+    int result = std::char_traits<Char>::compare(data_, other.data_, str_size);
+    if (result == 0)
+      result = size_ == other.size_ ? 0 : (size_ < other.size_ ? -1 : 1);
+    return result;
+  }
+
+  friend bool operator==(basic_string_view lhs, basic_string_view rhs) {
+    return lhs.compare(rhs) == 0;
+  }
+  friend bool operator!=(basic_string_view lhs, basic_string_view rhs) {
+    return lhs.compare(rhs) != 0;
+  }
+  friend bool operator<(basic_string_view lhs, basic_string_view rhs) {
+    return lhs.compare(rhs) < 0;
+  }
+  friend bool operator<=(basic_string_view lhs, basic_string_view rhs) {
+    return lhs.compare(rhs) <= 0;
+  }
+  friend bool operator>(basic_string_view lhs, basic_string_view rhs) {
+    return lhs.compare(rhs) > 0;
+  }
+  friend bool operator>=(basic_string_view lhs, basic_string_view rhs) {
+    return lhs.compare(rhs) >= 0;
+  }
+};
+
+using string_view = basic_string_view<char>;
+using wstring_view = basic_string_view<wchar_t>;
+
+/** Specifies if ``T`` is a character type. Can be specialized by users. */
+template <typename T> struct is_char : std::false_type {};
+template <> struct is_char<char> : std::true_type {};
+template <> struct is_char<wchar_t> : std::true_type {};
+template <> struct is_char<detail::char8_type> : std::true_type {};
+template <> struct is_char<char16_t> : std::true_type {};
+template <> struct is_char<char32_t> : std::true_type {};
+
+/**
+  \rst
+  Returns a string view of `s`. In order to add custom string type support to
+  {fmt} provide an overload of `to_string_view` for it in the same namespace as
+  the type for the argument-dependent lookup to work.
+
+  **Example**::
+
+    namespace my_ns {
+    inline string_view to_string_view(const my_string& s) {
+      return {s.data(), s.length()};
+    }
+    }
+    std::string message = fmt::format(my_string("The answer is {}"), 42);
+  \endrst
+ */
+template <typename Char, FMT_ENABLE_IF(is_char<Char>::value)>
+inline basic_string_view<Char> to_string_view(const Char* s) {
+  return s;
+}
+
+template <typename Char, typename Traits, typename Alloc>
+inline basic_string_view<Char> to_string_view(
+    const std::basic_string<Char, Traits, Alloc>& s) {
+  return s;
+}
+
+template <typename Char>
+inline basic_string_view<Char> to_string_view(basic_string_view<Char> s) {
+  return s;
+}
+
+template <typename Char,
+          FMT_ENABLE_IF(!std::is_empty<detail::std_string_view<Char>>::value)>
+inline basic_string_view<Char> to_string_view(detail::std_string_view<Char> s) {
+  return s;
+}
+
+// A base class for compile-time strings. It is defined in the fmt namespace to
+// make formatting functions visible via ADL, e.g. format(FMT_STRING("{}"), 42).
+struct compile_string {};
+
+template <typename S>
+struct is_compile_string : std::is_base_of<compile_string, S> {};
+
+template <typename S, FMT_ENABLE_IF(is_compile_string<S>::value)>
+constexpr basic_string_view<typename S::char_type> to_string_view(const S& s) {
+  return s;
+}
+
+namespace detail {
+void to_string_view(...);
+using fmt::v7::to_string_view;
+
+// Specifies whether S is a string type convertible to fmt::basic_string_view.
+// It should be a constexpr function but MSVC 2017 fails to compile it in
+// enable_if and MSVC 2015 fails to compile it as an alias template.
+template <typename S>
+struct is_string : std::is_class<decltype(to_string_view(std::declval<S>()))> {
+};
+
+template <typename S, typename = void> struct char_t_impl {};
+template <typename S> struct char_t_impl<S, enable_if_t<is_string<S>::value>> {
+  using result = decltype(to_string_view(std::declval<S>()));
+  using type = typename result::value_type;
+};
+
+struct error_handler {
+  constexpr error_handler() = default;
+  constexpr error_handler(const error_handler&) = default;
+
+  // This function is intentionally not constexpr to give a compile-time error.
+  FMT_NORETURN FMT_API void on_error(const char* message);
+};
+}  // namespace detail
+
+/** String's character type. */
+template <typename S> using char_t = typename detail::char_t_impl<S>::type;
+
+/**
+  \rst
+  Parsing context consisting of a format string range being parsed and an
+  argument counter for automatic indexing.
+
+  You can use one of the following type aliases for common character types:
+
+  +-----------------------+-------------------------------------+
+  | Type                  | Definition                          |
+  +=======================+=====================================+
+  | format_parse_context  | basic_format_parse_context<char>    |
+  +-----------------------+-------------------------------------+
+  | wformat_parse_context | basic_format_parse_context<wchar_t> |
+  +-----------------------+-------------------------------------+
+  \endrst
+ */
+template <typename Char, typename ErrorHandler = detail::error_handler>
+class basic_format_parse_context : private ErrorHandler {
+ private:
+  basic_string_view<Char> format_str_;
+  int next_arg_id_;
+
+ public:
+  using char_type = Char;
+  using iterator = typename basic_string_view<Char>::iterator;
+
+  explicit constexpr basic_format_parse_context(
+      basic_string_view<Char> format_str, ErrorHandler eh = {})
+      : ErrorHandler(eh), format_str_(format_str), next_arg_id_(0) {}
+
+  /**
+    Returns an iterator to the beginning of the format string range being
+    parsed.
+   */
+  constexpr iterator begin() const FMT_NOEXCEPT { return format_str_.begin(); }
+
+  /**
+    Returns an iterator past the end of the format string range being parsed.
+   */
+  constexpr iterator end() const FMT_NOEXCEPT { return format_str_.end(); }
+
+  /** Advances the begin iterator to ``it``. */
+  FMT_CONSTEXPR void advance_to(iterator it) {
+    format_str_.remove_prefix(detail::to_unsigned(it - begin()));
+  }
+
+  /**
+    Reports an error if using the manual argument indexing; otherwise returns
+    the next argument index and switches to the automatic indexing.
+   */
+  FMT_CONSTEXPR int next_arg_id() {
+    // Don't check if the argument id is valid to avoid overhead and because it
+    // will be checked during formatting anyway.
+    if (next_arg_id_ >= 0) return next_arg_id_++;
+    on_error("cannot switch from manual to automatic argument indexing");
+    return 0;
+  }
+
+  /**
+    Reports an error if using the automatic argument indexing; otherwise
+    switches to the manual indexing.
+   */
+  FMT_CONSTEXPR void check_arg_id(int) {
+    if (next_arg_id_ > 0)
+      on_error("cannot switch from automatic to manual argument indexing");
+    else
+      next_arg_id_ = -1;
+  }
+
+  FMT_CONSTEXPR void check_arg_id(basic_string_view<Char>) {}
+
+  FMT_CONSTEXPR void on_error(const char* message) {
+    ErrorHandler::on_error(message);
+  }
+
+  constexpr ErrorHandler error_handler() const { return *this; }
+};
+
+using format_parse_context = basic_format_parse_context<char>;
+using wformat_parse_context = basic_format_parse_context<wchar_t>;
+
+template <typename Context> class basic_format_arg;
+template <typename Context> class basic_format_args;
+template <typename Context> class dynamic_format_arg_store;
+
+// A formatter for objects of type T.
+template <typename T, typename Char = char, typename Enable = void>
+struct formatter {
+  // A deleted default constructor indicates a disabled formatter.
+  formatter() = delete;
+};
+
+// Specifies if T has an enabled formatter specialization. A type can be
+// formattable even if it doesn't have a formatter e.g. via a conversion.
+template <typename T, typename Context>
+using has_formatter =
+    std::is_constructible<typename Context::template formatter_type<T>>;
+
+namespace detail {
+
+/**
+  \rst
+  A contiguous memory buffer with an optional growing ability. It is an internal
+  class and shouldn't be used directly, only via `~fmt::basic_memory_buffer`.
+  \endrst
+ */
+template <typename T> class buffer {
+ private:
+  T* ptr_;
+  size_t size_;
+  size_t capacity_;
+
+ protected:
+  // Don't initialize ptr_ since it is not accessed to save a few cycles.
+  FMT_SUPPRESS_MSC_WARNING(26495)
+  buffer(size_t sz) FMT_NOEXCEPT : size_(sz), capacity_(sz) {}
+
+  buffer(T* p = nullptr, size_t sz = 0, size_t cap = 0) FMT_NOEXCEPT
+      : ptr_(p),
+        size_(sz),
+        capacity_(cap) {}
+
+  /** Sets the buffer data and capacity. */
+  void set(T* buf_data, size_t buf_capacity) FMT_NOEXCEPT {
+    ptr_ = buf_data;
+    capacity_ = buf_capacity;
+  }
+
+  /** Increases the buffer capacity to hold at least *capacity* elements. */
+  virtual void grow(size_t capacity) = 0;
+
+ public:
+  using value_type = T;
+  using const_reference = const T&;
+
+  buffer(const buffer&) = delete;
+  void operator=(const buffer&) = delete;
+  virtual ~buffer() = default;
+
+  T* begin() FMT_NOEXCEPT { return ptr_; }
+  T* end() FMT_NOEXCEPT { return ptr_ + size_; }
+
+  const T* begin() const FMT_NOEXCEPT { return ptr_; }
+  const T* end() const FMT_NOEXCEPT { return ptr_ + size_; }
+
+  /** Returns the size of this buffer. */
+  size_t size() const FMT_NOEXCEPT { return size_; }
+
+  /** Returns the capacity of this buffer. */
+  size_t capacity() const FMT_NOEXCEPT { return capacity_; }
+
+  /** Returns a pointer to the buffer data. */
+  T* data() FMT_NOEXCEPT { return ptr_; }
+
+  /** Returns a pointer to the buffer data. */
+  const T* data() const FMT_NOEXCEPT { return ptr_; }
+
+  /**
+    Resizes the buffer. If T is a POD type new elements may not be initialized.
+   */
+  void resize(size_t new_size) {
+    reserve(new_size);
+    size_ = new_size;
+  }
+
+  /** Clears this buffer. */
+  void clear() { size_ = 0; }
+
+  /** Reserves space to store at least *capacity* elements. */
+  void reserve(size_t new_capacity) {
+    if (new_capacity > capacity_) grow(new_capacity);
+  }
+
+  void push_back(const T& value) {
+    reserve(size_ + 1);
+    ptr_[size_++] = value;
+  }
+
+  /** Appends data to the end of the buffer. */
+  template <typename U> void append(const U* begin, const U* end);
+
+  template <typename I> T& operator[](I index) { return ptr_[index]; }
+  template <typename I> const T& operator[](I index) const {
+    return ptr_[index];
+  }
+};
+
+// A container-backed buffer.
+template <typename Container>
+class container_buffer : public buffer<typename Container::value_type> {
+ private:
+  Container& container_;
+
+ protected:
+  void grow(size_t capacity) FMT_OVERRIDE {
+    container_.resize(capacity);
+    this->set(&container_[0], capacity);
+  }
+
+ public:
+  explicit container_buffer(Container& c)
+      : buffer<typename Container::value_type>(c.size()), container_(c) {}
+};
+
+// Extracts a reference to the container from back_insert_iterator.
+template <typename Container>
+inline Container& get_container(std::back_insert_iterator<Container> it) {
+  using bi_iterator = std::back_insert_iterator<Container>;
+  struct accessor : bi_iterator {
+    accessor(bi_iterator iter) : bi_iterator(iter) {}
+    using bi_iterator::container;
+  };
+  return *accessor(it).container;
+}
+
+template <typename T, typename Char = char, typename Enable = void>
+struct fallback_formatter {
+  fallback_formatter() = delete;
+};
+
+// Specifies if T has an enabled fallback_formatter specialization.
+template <typename T, typename Context>
+using has_fallback_formatter =
+    std::is_constructible<fallback_formatter<T, typename Context::char_type>>;
+
+struct view {};
+
+template <typename Char, typename T> struct named_arg : view {
+  const Char* name;
+  const T& value;
+  named_arg(const Char* n, const T& v) : name(n), value(v) {}
+};
+
+template <typename Char> struct named_arg_info {
+  const Char* name;
+  int id;
+};
+
+template <typename T, typename Char, size_t NUM_ARGS, size_t NUM_NAMED_ARGS>
+struct arg_data {
+  // args_[0].named_args points to named_args_ to avoid bloating format_args.
+  T args_[1 + (NUM_ARGS != 0 ? NUM_ARGS : 1)];
+  named_arg_info<Char> named_args_[NUM_NAMED_ARGS];
+
+  template <typename... U>
+  arg_data(const U&... init) : args_{T(named_args_, NUM_NAMED_ARGS), init...} {}
+  arg_data(const arg_data& other) = delete;
+  const T* args() const { return args_ + 1; }
+  named_arg_info<Char>* named_args() { return named_args_; }
+};
+
+template <typename T, typename Char, size_t NUM_ARGS>
+struct arg_data<T, Char, NUM_ARGS, 0> {
+  T args_[NUM_ARGS != 0 ? NUM_ARGS : 1];
+
+  template <typename... U>
+  FMT_INLINE arg_data(const U&... init) : args_{init...} {}
+  FMT_INLINE const T* args() const { return args_; }
+  FMT_INLINE std::nullptr_t named_args() { return nullptr; }
+};
+
+template <typename Char>
+inline void init_named_args(named_arg_info<Char>*, int, int) {}
+
+template <typename Char, typename T, typename... Tail>
+void init_named_args(named_arg_info<Char>* named_args, int arg_count,
+                     int named_arg_count, const T&, const Tail&... args) {
+  init_named_args(named_args, arg_count + 1, named_arg_count, args...);
+}
+
+template <typename Char, typename T, typename... Tail>
+void init_named_args(named_arg_info<Char>* named_args, int arg_count,
+                     int named_arg_count, const named_arg<Char, T>& arg,
+                     const Tail&... args) {
+  named_args[named_arg_count++] = {arg.name, arg_count};
+  init_named_args(named_args, arg_count + 1, named_arg_count, args...);
+}
+
+template <typename... Args>
+FMT_INLINE void init_named_args(std::nullptr_t, int, int, const Args&...) {}
+
+template <typename T> struct is_named_arg : std::false_type {};
+
+template <typename T, typename Char>
+struct is_named_arg<named_arg<Char, T>> : std::true_type {};
+
+template <bool B = false> constexpr size_t count() { return B ? 1 : 0; }
+template <bool B1, bool B2, bool... Tail> constexpr size_t count() {
+  return (B1 ? 1 : 0) + count<B2, Tail...>();
+}
+
+template <typename... Args> constexpr size_t count_named_args() {
+  return count<is_named_arg<Args>::value...>();
+}
+
+enum class type {
+  none_type,
+  // Integer types should go first,
+  int_type,
+  uint_type,
+  long_long_type,
+  ulong_long_type,
+  int128_type,
+  uint128_type,
+  bool_type,
+  char_type,
+  last_integer_type = char_type,
+  // followed by floating-point types.
+  float_type,
+  double_type,
+  long_double_type,
+  last_numeric_type = long_double_type,
+  cstring_type,
+  string_type,
+  pointer_type,
+  custom_type
+};
+
+// Maps core type T to the corresponding type enum constant.
+template <typename T, typename Char>
+struct type_constant : std::integral_constant<type, type::custom_type> {};
+
+#define FMT_TYPE_CONSTANT(Type, constant) \
+  template <typename Char>                \
+  struct type_constant<Type, Char>        \
+      : std::integral_constant<type, type::constant> {}
+
+FMT_TYPE_CONSTANT(int, int_type);
+FMT_TYPE_CONSTANT(unsigned, uint_type);
+FMT_TYPE_CONSTANT(long long, long_long_type);
+FMT_TYPE_CONSTANT(unsigned long long, ulong_long_type);
+FMT_TYPE_CONSTANT(int128_t, int128_type);
+FMT_TYPE_CONSTANT(uint128_t, uint128_type);
+FMT_TYPE_CONSTANT(bool, bool_type);
+FMT_TYPE_CONSTANT(Char, char_type);
+FMT_TYPE_CONSTANT(float, float_type);
+FMT_TYPE_CONSTANT(double, double_type);
+FMT_TYPE_CONSTANT(long double, long_double_type);
+FMT_TYPE_CONSTANT(const Char*, cstring_type);
+FMT_TYPE_CONSTANT(basic_string_view<Char>, string_type);
+FMT_TYPE_CONSTANT(const void*, pointer_type);
+
+constexpr bool is_integral_type(type t) {
+  return t > type::none_type && t <= type::last_integer_type;
+}
+
+constexpr bool is_arithmetic_type(type t) {
+  return t > type::none_type && t <= type::last_numeric_type;
+}
+
+template <typename Char> struct string_value {
+  const Char* data;
+  size_t size;
+};
+
+template <typename Char> struct named_arg_value {
+  const named_arg_info<Char>* data;
+  size_t size;
+};
+
+template <typename Context> struct custom_value {
+  using parse_context = typename Context::parse_context_type;
+  const void* value;
+  void (*format)(const void* arg, parse_context& parse_ctx, Context& ctx);
+};
+
+// A formatting argument value.
+template <typename Context> class value {
+ public:
+  using char_type = typename Context::char_type;
+
+  union {
+    int int_value;
+    unsigned uint_value;
+    long long long_long_value;
+    unsigned long long ulong_long_value;
+    int128_t int128_value;
+    uint128_t uint128_value;
+    bool bool_value;
+    char_type char_value;
+    float float_value;
+    double double_value;
+    long double long_double_value;
+    const void* pointer;
+    string_value<char_type> string;
+    custom_value<Context> custom;
+    named_arg_value<char_type> named_args;
+  };
+
+  constexpr FMT_INLINE value(int val = 0) : int_value(val) {}
+  constexpr FMT_INLINE value(unsigned val) : uint_value(val) {}
+  FMT_INLINE value(long long val) : long_long_value(val) {}
+  FMT_INLINE value(unsigned long long val) : ulong_long_value(val) {}
+  FMT_INLINE value(int128_t val) : int128_value(val) {}
+  FMT_INLINE value(uint128_t val) : uint128_value(val) {}
+  FMT_INLINE value(float val) : float_value(val) {}
+  FMT_INLINE value(double val) : double_value(val) {}
+  FMT_INLINE value(long double val) : long_double_value(val) {}
+  FMT_INLINE value(bool val) : bool_value(val) {}
+  FMT_INLINE value(char_type val) : char_value(val) {}
+  FMT_INLINE value(const char_type* val) { string.data = val; }
+  FMT_INLINE value(basic_string_view<char_type> val) {
+    string.data = val.data();
+    string.size = val.size();
+  }
+  FMT_INLINE value(const void* val) : pointer(val) {}
+  FMT_INLINE value(const named_arg_info<char_type>* args, size_t size)
+      : named_args{args, size} {}
+
+  template <typename T> FMT_INLINE value(const T& val) {
+    custom.value = &val;
+    // Get the formatter type through the context to allow different contexts
+    // have different extension points, e.g. `formatter<T>` for `format` and
+    // `printf_formatter<T>` for `printf`.
+    custom.format = format_custom_arg<
+        T, conditional_t<has_formatter<T, Context>::value,
+                         typename Context::template formatter_type<T>,
+                         fallback_formatter<T, char_type>>>;
+  }
+
+ private:
+  // Formats an argument of a custom type, such as a user-defined class.
+  template <typename T, typename Formatter>
+  static void format_custom_arg(const void* arg,
+                                typename Context::parse_context_type& parse_ctx,
+                                Context& ctx) {
+    Formatter f;
+    parse_ctx.advance_to(f.parse(parse_ctx));
+    ctx.advance_to(f.format(*static_cast<const T*>(arg), ctx));
+  }
+};
+
+template <typename Context, typename T>
+FMT_CONSTEXPR basic_format_arg<Context> make_arg(const T& value);
+
+// To minimize the number of types we need to deal with, long is translated
+// either to int or to long long depending on its size.
+enum { long_short = sizeof(long) == sizeof(int) };
+using long_type = conditional_t<long_short, int, long long>;
+using ulong_type = conditional_t<long_short, unsigned, unsigned long long>;
+
+// Maps formatting arguments to core types.
+template <typename Context> struct arg_mapper {
+  using char_type = typename Context::char_type;
+
+  FMT_CONSTEXPR int map(signed char val) { return val; }
+  FMT_CONSTEXPR unsigned map(unsigned char val) { return val; }
+  FMT_CONSTEXPR int map(short val) { return val; }
+  FMT_CONSTEXPR unsigned map(unsigned short val) { return val; }
+  FMT_CONSTEXPR int map(int val) { return val; }
+  FMT_CONSTEXPR unsigned map(unsigned val) { return val; }
+  FMT_CONSTEXPR long_type map(long val) { return val; }
+  FMT_CONSTEXPR ulong_type map(unsigned long val) { return val; }
+  FMT_CONSTEXPR long long map(long long val) { return val; }
+  FMT_CONSTEXPR unsigned long long map(unsigned long long val) { return val; }
+  FMT_CONSTEXPR int128_t map(int128_t val) { return val; }
+  FMT_CONSTEXPR uint128_t map(uint128_t val) { return val; }
+  FMT_CONSTEXPR bool map(bool val) { return val; }
+
+  template <typename T, FMT_ENABLE_IF(is_char<T>::value)>
+  FMT_CONSTEXPR char_type map(T val) {
+    static_assert(
+        std::is_same<T, char>::value || std::is_same<T, char_type>::value,
+        "mixing character types is disallowed");
+    return val;
+  }
+
+  FMT_CONSTEXPR float map(float val) { return val; }
+  FMT_CONSTEXPR double map(double val) { return val; }
+  FMT_CONSTEXPR long double map(long double val) { return val; }
+
+  FMT_CONSTEXPR const char_type* map(char_type* val) { return val; }
+  FMT_CONSTEXPR const char_type* map(const char_type* val) { return val; }
+  template <typename T, FMT_ENABLE_IF(is_string<T>::value)>
+  FMT_CONSTEXPR basic_string_view<char_type> map(const T& val) {
+    static_assert(std::is_same<char_type, char_t<T>>::value,
+                  "mixing character types is disallowed");
+    return to_string_view(val);
+  }
+  template <typename T,
+            FMT_ENABLE_IF(
+                std::is_constructible<basic_string_view<char_type>, T>::value &&
+                !is_string<T>::value && !has_formatter<T, Context>::value &&
+                !has_fallback_formatter<T, Context>::value)>
+  FMT_CONSTEXPR basic_string_view<char_type> map(const T& val) {
+    return basic_string_view<char_type>(val);
+  }
+  template <
+      typename T,
+      FMT_ENABLE_IF(
+          std::is_constructible<std_string_view<char_type>, T>::value &&
+          !std::is_constructible<basic_string_view<char_type>, T>::value &&
+          !is_string<T>::value && !has_formatter<T, Context>::value &&
+          !has_fallback_formatter<T, Context>::value)>
+  FMT_CONSTEXPR basic_string_view<char_type> map(const T& val) {
+    return std_string_view<char_type>(val);
+  }
+  FMT_CONSTEXPR const char* map(const signed char* val) {
+    static_assert(std::is_same<char_type, char>::value, "invalid string type");
+    return reinterpret_cast<const char*>(val);
+  }
+  FMT_CONSTEXPR const char* map(const unsigned char* val) {
+    static_assert(std::is_same<char_type, char>::value, "invalid string type");
+    return reinterpret_cast<const char*>(val);
+  }
+  FMT_CONSTEXPR const char* map(signed char* val) {
+    const auto* const_val = val;
+    return map(const_val);
+  }
+  FMT_CONSTEXPR const char* map(unsigned char* val) {
+    const auto* const_val = val;
+    return map(const_val);
+  }
+
+  FMT_CONSTEXPR const void* map(void* val) { return val; }
+  FMT_CONSTEXPR const void* map(const void* val) { return val; }
+  FMT_CONSTEXPR const void* map(std::nullptr_t val) { return val; }
+  template <typename T> FMT_CONSTEXPR int map(const T*) {
+    // Formatting of arbitrary pointers is disallowed. If you want to output
+    // a pointer cast it to "void *" or "const void *". In particular, this
+    // forbids formatting of "[const] volatile char *" which is printed as bool
+    // by iostreams.
+    static_assert(!sizeof(T), "formatting of non-void pointers is disallowed");
+    return 0;
+  }
+
+  template <typename T,
+            FMT_ENABLE_IF(std::is_enum<T>::value &&
+                          !has_formatter<T, Context>::value &&
+                          !has_fallback_formatter<T, Context>::value)>
+  FMT_CONSTEXPR auto map(const T& val)
+      -> decltype(std::declval<arg_mapper>().map(
+          static_cast<typename std::underlying_type<T>::type>(val))) {
+    return map(static_cast<typename std::underlying_type<T>::type>(val));
+  }
+  template <typename T,
+            FMT_ENABLE_IF(!is_string<T>::value && !is_char<T>::value &&
+                          (has_formatter<T, Context>::value ||
+                           has_fallback_formatter<T, Context>::value))>
+  FMT_CONSTEXPR const T& map(const T& val) {
+    return val;
+  }
+
+  template <typename T>
+  FMT_CONSTEXPR auto map(const named_arg<char_type, T>& val)
+      -> decltype(std::declval<arg_mapper>().map(val.value)) {
+    return map(val.value);
+  }
+
+  int map(...) {
+    constexpr bool formattable = sizeof(Context) == 0;
+    static_assert(
+        formattable,
+        "Cannot format argument. To make type T formattable provide a "
+        "formatter<T> specialization: "
+        "https://fmt.dev/latest/api.html#formatting-user-defined-types");
+    return 0;
+  }
+};
+
+// A type constant after applying arg_mapper<Context>.
+template <typename T, typename Context>
+using mapped_type_constant =
+    type_constant<decltype(arg_mapper<Context>().map(std::declval<const T&>())),
+                  typename Context::char_type>;
+
+enum { packed_arg_bits = 4 };
+// Maximum number of arguments with packed types.
+enum { max_packed_args = 62 / packed_arg_bits };
+enum : unsigned long long { is_unpacked_bit = 1ULL << 63 };
+enum : unsigned long long { has_named_args_bit = 1ULL << 62 };
+}  // namespace detail
+
+// A formatting argument. It is a trivially copyable/constructible type to
+// allow storage in basic_memory_buffer.
+template <typename Context> class basic_format_arg {
+ private:
+  detail::value<Context> value_;
+  detail::type type_;
+
+  template <typename ContextType, typename T>
+  friend FMT_CONSTEXPR basic_format_arg<ContextType> detail::make_arg(
+      const T& value);
+
+  template <typename Visitor, typename Ctx>
+  friend FMT_CONSTEXPR auto visit_format_arg(Visitor&& vis,
+                                             const basic_format_arg<Ctx>& arg)
+      -> decltype(vis(0));
+
+  friend class basic_format_args<Context>;
+  friend class dynamic_format_arg_store<Context>;
+
+  using char_type = typename Context::char_type;
+
+  template <typename T, typename Char, size_t NUM_ARGS, size_t NUM_NAMED_ARGS>
+  friend struct detail::arg_data;
+
+  basic_format_arg(const detail::named_arg_info<char_type>* args, size_t size)
+      : value_(args, size) {}
+
+ public:
+  class handle {
+   public:
+    explicit handle(detail::custom_value<Context> custom) : custom_(custom) {}
+
+    void format(typename Context::parse_context_type& parse_ctx,
+                Context& ctx) const {
+      custom_.format(custom_.value, parse_ctx, ctx);
+    }
+
+   private:
+    detail::custom_value<Context> custom_;
+  };
+
+  constexpr basic_format_arg() : type_(detail::type::none_type) {}
+
+  constexpr explicit operator bool() const FMT_NOEXCEPT {
+    return type_ != detail::type::none_type;
+  }
+
+  detail::type type() const { return type_; }
+
+  bool is_integral() const { return detail::is_integral_type(type_); }
+  bool is_arithmetic() const { return detail::is_arithmetic_type(type_); }
+};
+
+/**
+  \rst
+  Visits an argument dispatching to the appropriate visit method based on
+  the argument type. For example, if the argument type is ``double`` then
+  ``vis(value)`` will be called with the value of type ``double``.
+  \endrst
+ */
+template <typename Visitor, typename Context>
+FMT_CONSTEXPR_DECL FMT_INLINE auto visit_format_arg(
+    Visitor&& vis, const basic_format_arg<Context>& arg) -> decltype(vis(0)) {
+  using char_type = typename Context::char_type;
+  switch (arg.type_) {
+  case detail::type::none_type:
+    break;
+  case detail::type::int_type:
+    return vis(arg.value_.int_value);
+  case detail::type::uint_type:
+    return vis(arg.value_.uint_value);
+  case detail::type::long_long_type:
+    return vis(arg.value_.long_long_value);
+  case detail::type::ulong_long_type:
+    return vis(arg.value_.ulong_long_value);
+#if FMT_USE_INT128
+  case detail::type::int128_type:
+    return vis(arg.value_.int128_value);
+  case detail::type::uint128_type:
+    return vis(arg.value_.uint128_value);
+#else
+  case detail::type::int128_type:
+  case detail::type::uint128_type:
+    break;
+#endif
+  case detail::type::bool_type:
+    return vis(arg.value_.bool_value);
+  case detail::type::char_type:
+    return vis(arg.value_.char_value);
+  case detail::type::float_type:
+    return vis(arg.value_.float_value);
+  case detail::type::double_type:
+    return vis(arg.value_.double_value);
+  case detail::type::long_double_type:
+    return vis(arg.value_.long_double_value);
+  case detail::type::cstring_type:
+    return vis(arg.value_.string.data);
+  case detail::type::string_type:
+    return vis(basic_string_view<char_type>(arg.value_.string.data,
+                                            arg.value_.string.size));
+  case detail::type::pointer_type:
+    return vis(arg.value_.pointer);
+  case detail::type::custom_type:
+    return vis(typename basic_format_arg<Context>::handle(arg.value_.custom));
+  }
+  return vis(monostate());
+}
+
+// Checks whether T is a container with contiguous storage.
+template <typename T> struct is_contiguous : std::false_type {};
+template <typename Char>
+struct is_contiguous<std::basic_string<Char>> : std::true_type {};
+template <typename Char>
+struct is_contiguous<detail::buffer<Char>> : std::true_type {};
+
+namespace detail {
+
+template <typename OutputIt>
+struct is_back_insert_iterator : std::false_type {};
+template <typename Container>
+struct is_back_insert_iterator<std::back_insert_iterator<Container>>
+    : std::true_type {};
+
+template <typename OutputIt>
+struct is_contiguous_back_insert_iterator : std::false_type {};
+template <typename Container>
+struct is_contiguous_back_insert_iterator<std::back_insert_iterator<Container>>
+    : is_contiguous<Container> {};
+
+// A type-erased reference to an std::locale to avoid heavy <locale> include.
+class locale_ref {
+ private:
+  const void* locale_;  // A type-erased pointer to std::locale.
+
+ public:
+  locale_ref() : locale_(nullptr) {}
+  template <typename Locale> explicit locale_ref(const Locale& loc);
+
+  explicit operator bool() const FMT_NOEXCEPT { return locale_ != nullptr; }
+
+  template <typename Locale> Locale get() const;
+};
+
+template <typename> constexpr unsigned long long encode_types() { return 0; }
+
+template <typename Context, typename Arg, typename... Args>
+constexpr unsigned long long encode_types() {
+  return static_cast<unsigned>(mapped_type_constant<Arg, Context>::value) |
+         (encode_types<Context, Args...>() << packed_arg_bits);
+}
+
+template <typename Context, typename T>
+FMT_CONSTEXPR basic_format_arg<Context> make_arg(const T& value) {
+  basic_format_arg<Context> arg;
+  arg.type_ = mapped_type_constant<T, Context>::value;
+  arg.value_ = arg_mapper<Context>().map(value);
+  return arg;
+}
+
+// The type template parameter is there to avoid an ODR violation when using
+// a fallback formatter in one translation unit and an implicit conversion in
+// another (not recommended).
+template <bool IS_PACKED, typename Context, type, typename T,
+          FMT_ENABLE_IF(IS_PACKED)>
+inline value<Context> make_arg(const T& val) {
+  return arg_mapper<Context>().map(val);
+}
+
+template <bool IS_PACKED, typename Context, type, typename T,
+          FMT_ENABLE_IF(!IS_PACKED)>
+inline basic_format_arg<Context> make_arg(const T& value) {
+  return make_arg<Context>(value);
+}
+
+template <typename T> struct is_reference_wrapper : std::false_type {};
+template <typename T>
+struct is_reference_wrapper<std::reference_wrapper<T>> : std::true_type {};
+
+template <typename T> const T& unwrap(const T& v) { return v; }
+template <typename T> const T& unwrap(const std::reference_wrapper<T>& v) {
+  return static_cast<const T&>(v);
+}
+
+class dynamic_arg_list {
+  // Workaround for clang's -Wweak-vtables. Unlike for regular classes, for
+  // templates it doesn't complain about inability to deduce single translation
+  // unit for placing vtable. So storage_node_base is made a fake template.
+  template <typename = void> struct node {
+    virtual ~node() = default;
+    std::unique_ptr<node<>> next;
+  };
+
+  template <typename T> struct typed_node : node<> {
+    T value;
+
+    template <typename Arg>
+    FMT_CONSTEXPR typed_node(const Arg& arg) : value(arg) {}
+
+    template <typename Char>
+    FMT_CONSTEXPR typed_node(const basic_string_view<Char>& arg)
+        : value(arg.data(), arg.size()) {}
+  };
+
+  std::unique_ptr<node<>> head_;
+
+ public:
+  template <typename T, typename Arg> const T& push(const Arg& arg) {
+    auto new_node = std::unique_ptr<typed_node<T>>(new typed_node<T>(arg));
+    auto& value = new_node->value;
+    new_node->next = std::move(head_);
+    head_ = std::move(new_node);
+    return value;
+  }
+};
+}  // namespace detail
+
+// Formatting context.
+template <typename OutputIt, typename Char> class basic_format_context {
+ public:
+  /** The character type for the output. */
+  using char_type = Char;
+
+ private:
+  OutputIt out_;
+  basic_format_args<basic_format_context> args_;
+  detail::locale_ref loc_;
+
+ public:
+  using iterator = OutputIt;
+  using format_arg = basic_format_arg<basic_format_context>;
+  using parse_context_type = basic_format_parse_context<Char>;
+  template <typename T> using formatter_type = formatter<T, char_type>;
+
+  basic_format_context(const basic_format_context&) = delete;
+  void operator=(const basic_format_context&) = delete;
+  /**
+   Constructs a ``basic_format_context`` object. References to the arguments are
+   stored in the object so make sure they have appropriate lifetimes.
+   */
+  basic_format_context(OutputIt out,
+                       basic_format_args<basic_format_context> ctx_args,
+                       detail::locale_ref loc = detail::locale_ref())
+      : out_(out), args_(ctx_args), loc_(loc) {}
+
+  format_arg arg(int id) const { return args_.get(id); }
+  format_arg arg(basic_string_view<char_type> name) { return args_.get(name); }
+  int arg_id(basic_string_view<char_type> name) { return args_.get_id(name); }
+  const basic_format_args<basic_format_context>& args() const { return args_; }
+
+  detail::error_handler error_handler() { return {}; }
+  void on_error(const char* message) { error_handler().on_error(message); }
+
+  // Returns an iterator to the beginning of the output range.
+  iterator out() { return out_; }
+
+  // Advances the begin iterator to ``it``.
+  void advance_to(iterator it) {
+    if (!detail::is_back_insert_iterator<iterator>()) out_ = it;
+  }
+
+  detail::locale_ref locale() { return loc_; }
+};
+
+template <typename Char>
+using buffer_context =
+    basic_format_context<std::back_insert_iterator<detail::buffer<Char>>, Char>;
+using format_context = buffer_context<char>;
+using wformat_context = buffer_context<wchar_t>;
+
+// Workaround a bug in gcc: https://stackoverflow.com/q/62767544/471164.
+#define FMT_BUFFER_CONTEXT(Char) \
+  basic_format_context<std::back_insert_iterator<detail::buffer<Char>>, Char>
+
+/**
+  \rst
+  An array of references to arguments. It can be implicitly converted into
+  `~fmt::basic_format_args` for passing into type-erased formatting functions
+  such as `~fmt::vformat`.
+  \endrst
+ */
+template <typename Context, typename... Args>
+class format_arg_store
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
+    // Workaround a GCC template argument substitution bug.
+    : public basic_format_args<Context>
+#endif
+{
+ private:
+  static const size_t num_args = sizeof...(Args);
+  static const size_t num_named_args = detail::count_named_args<Args...>();
+  static const bool is_packed = num_args <= detail::max_packed_args;
+
+  using value_type = conditional_t<is_packed, detail::value<Context>,
+                                   basic_format_arg<Context>>;
+
+  detail::arg_data<value_type, typename Context::char_type, num_args,
+                   num_named_args>
+      data_;
+
+  friend class basic_format_args<Context>;
+
+  static constexpr unsigned long long desc =
+      (is_packed ? detail::encode_types<Context, Args...>()
+                 : detail::is_unpacked_bit | num_args) |
+      (num_named_args != 0
+           ? static_cast<unsigned long long>(detail::has_named_args_bit)
+           : 0);
+
+ public:
+  format_arg_store(const Args&... args)
+      :
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
+        basic_format_args<Context>(*this),
+#endif
+        data_{detail::make_arg<
+            is_packed, Context,
+            detail::mapped_type_constant<Args, Context>::value>(args)...} {
+    detail::init_named_args(data_.named_args(), 0, 0, args...);
+  }
+};
+
+/**
+  \rst
+  Constructs an `~fmt::format_arg_store` object that contains references to
+  arguments and can be implicitly converted to `~fmt::format_args`. `Context`
+  can be omitted in which case it defaults to `~fmt::context`.
+  See `~fmt::arg` for lifetime considerations.
+  \endrst
+ */
+template <typename Context = format_context, typename... Args>
+inline format_arg_store<Context, Args...> make_format_args(
+    const Args&... args) {
+  return {args...};
+}
+
+/**
+  \rst
+  Returns a named argument to be used in a formatting function. It should only
+  be used in a call to a formatting function.
+
+  **Example**::
+
+    fmt::print("Elapsed time: {s:.2f} seconds", fmt::arg("s", 1.23));
+  \endrst
+ */
+template <typename Char, typename T>
+inline detail::named_arg<Char, T> arg(const Char* name, const T& arg) {
+  static_assert(!detail::is_named_arg<T>(), "nested named arguments");
+  return {name, arg};
+}
+
+/**
+  \rst
+  A dynamic version of `fmt::format_arg_store`.
+  It's equipped with a storage to potentially temporary objects which lifetimes
+  could be shorter than the format arguments object.
+
+  It can be implicitly converted into `~fmt::basic_format_args` for passing
+  into type-erased formatting functions such as `~fmt::vformat`.
+  \endrst
+ */
+template <typename Context>
+class dynamic_format_arg_store
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
+    // Workaround a GCC template argument substitution bug.
+    : public basic_format_args<Context>
+#endif
+{
+ private:
+  using char_type = typename Context::char_type;
+
+  template <typename T> struct need_copy {
+    static constexpr detail::type mapped_type =
+        detail::mapped_type_constant<T, Context>::value;
+
+    enum {
+      value = !(detail::is_reference_wrapper<T>::value ||
+                std::is_same<T, basic_string_view<char_type>>::value ||
+                std::is_same<T, detail::std_string_view<char_type>>::value ||
+                (mapped_type != detail::type::cstring_type &&
+                 mapped_type != detail::type::string_type &&
+                 mapped_type != detail::type::custom_type))
+    };
+  };
+
+  template <typename T>
+  using stored_type = conditional_t<detail::is_string<T>::value,
+                                    std::basic_string<char_type>, T>;
+
+  // Storage of basic_format_arg must be contiguous.
+  std::vector<basic_format_arg<Context>> data_;
+  std::vector<detail::named_arg_info<char_type>> named_info_;
+
+  // Storage of arguments not fitting into basic_format_arg must grow
+  // without relocation because items in data_ refer to it.
+  detail::dynamic_arg_list dynamic_args_;
+
+  friend class basic_format_args<Context>;
+
+  unsigned long long get_types() const {
+    return detail::is_unpacked_bit | data_.size() |
+           (named_info_.empty()
+                ? 0ULL
+                : static_cast<unsigned long long>(detail::has_named_args_bit));
+  }
+
+  const basic_format_arg<Context>* data() const {
+    return named_info_.empty() ? data_.data() : data_.data() + 1;
+  }
+
+  template <typename T> void emplace_arg(const T& arg) {
+    data_.emplace_back(detail::make_arg<Context>(arg));
+  }
+
+  template <typename T>
+  void emplace_arg(const detail::named_arg<char_type, T>& arg) {
+    if (named_info_.empty()) {
+      constexpr const detail::named_arg_info<char_type>* zero_ptr{nullptr};
+      data_.insert(data_.begin(), {zero_ptr, 0});
+    }
+    data_.emplace_back(detail::make_arg<Context>(detail::unwrap(arg.value)));
+    auto pop_one = [](std::vector<basic_format_arg<Context>>* data) {
+      data->pop_back();
+    };
+    std::unique_ptr<std::vector<basic_format_arg<Context>>, decltype(pop_one)>
+        guard{&data_, pop_one};
+    named_info_.push_back({arg.name, static_cast<int>(data_.size() - 2u)});
+    data_[0].value_.named_args = {named_info_.data(), named_info_.size()};
+    guard.release();
+  }
+
+ public:
+  /**
+    \rst
+    Adds an argument into the dynamic store for later passing to a formatting
+    function.
+
+    Note that custom types and string types (but not string views) are copied
+    into the store dynamically allocating memory if necessary.
+
+    **Example**::
+
+      fmt::dynamic_format_arg_store<fmt::format_context> store;
+      store.push_back(42);
+      store.push_back("abc");
+      store.push_back(1.5f);
+      std::string result = fmt::vformat("{} and {} and {}", store);
+    \endrst
+  */
+  template <typename T> void push_back(const T& arg) {
+    if (detail::const_check(need_copy<T>::value))
+      emplace_arg(dynamic_args_.push<stored_type<T>>(arg));
+    else
+      emplace_arg(detail::unwrap(arg));
+  }
+
+  /**
+    \rst
+    Adds a reference to the argument into the dynamic store for later passing to
+    a formatting function. Supports named arguments wrapped in
+    ``std::reference_wrapper`` via ``std::ref()``/``std::cref()``.
+
+    **Example**::
+
+      fmt::dynamic_format_arg_store<fmt::format_context> store;
+      char str[] = "1234567890";
+      store.push_back(std::cref(str));
+      int a1_val{42};
+      auto a1 = fmt::arg("a1_", a1_val);
+      store.push_back(std::cref(a1));
+
+      // Changing str affects the output but only for string and custom types.
+      str[0] = 'X';
+
+      std::string result = fmt::vformat("{} and {a1_}");
+      assert(result == "X234567890 and 42");
+    \endrst
+  */
+  template <typename T> void push_back(std::reference_wrapper<T> arg) {
+    static_assert(
+        detail::is_named_arg<typename std::remove_cv<T>::type>::value ||
+            need_copy<T>::value,
+        "objects of built-in types and string views are always copied");
+    emplace_arg(arg.get());
+  }
+
+  /**
+    Adds named argument into the dynamic store for later passing to a formatting
+    function. ``std::reference_wrapper`` is supported to avoid copying of the
+    argument.
+  */
+  template <typename T>
+  void push_back(const detail::named_arg<char_type, T>& arg) {
+    const char_type* arg_name =
+        dynamic_args_.push<std::basic_string<char_type>>(arg.name).c_str();
+    if (detail::const_check(need_copy<T>::value)) {
+      emplace_arg(
+          fmt::arg(arg_name, dynamic_args_.push<stored_type<T>>(arg.value)));
+    } else {
+      emplace_arg(fmt::arg(arg_name, arg.value));
+    }
+  }
+
+  /** Erase all elements from the store */
+  void clear() {
+    data_.clear();
+    named_info_.clear();
+    dynamic_args_ = detail::dynamic_arg_list();
+  }
+
+  /**
+    \rst
+    Reserves space to store at least *new_cap* arguments including
+    *new_cap_named* named arguments.
+    \endrst
+  */
+  void reserve(size_t new_cap, size_t new_cap_named) {
+    FMT_ASSERT(new_cap >= new_cap_named,
+               "Set of arguments includes set of named arguments");
+    data_.reserve(new_cap);
+    named_info_.reserve(new_cap_named);
+  }
+};
+
+/**
+  \rst
+  A view of a collection of formatting arguments. To avoid lifetime issues it
+  should only be used as a parameter type in type-erased functions such as
+  ``vformat``::
+
+    void vlog(string_view format_str, format_args args);  // OK
+    format_args args = make_format_args(42);  // Error: dangling reference
+  \endrst
+ */
+template <typename Context> class basic_format_args {
+ public:
+  using size_type = int;
+  using format_arg = basic_format_arg<Context>;
+
+ private:
+  // A descriptor that contains information about formatting arguments.
+  // If the number of arguments is less or equal to max_packed_args then
+  // argument types are passed in the descriptor. This reduces binary code size
+  // per formatting function call.
+  unsigned long long desc_;
+  union {
+    // If is_packed() returns true then argument values are stored in values_;
+    // otherwise they are stored in args_. This is done to improve cache
+    // locality and reduce compiled code size since storing larger objects
+    // may require more code (at least on x86-64) even if the same amount of
+    // data is actually copied to stack. It saves ~10% on the bloat test.
+    const detail::value<Context>* values_;
+    const format_arg* args_;
+  };
+
+  bool is_packed() const { return (desc_ & detail::is_unpacked_bit) == 0; }
+  bool has_named_args() const {
+    return (desc_ & detail::has_named_args_bit) != 0;
+  }
+
+  detail::type type(int index) const {
+    int shift = index * detail::packed_arg_bits;
+    unsigned int mask = (1 << detail::packed_arg_bits) - 1;
+    return static_cast<detail::type>((desc_ >> shift) & mask);
+  }
+
+  basic_format_args(unsigned long long desc,
+                    const detail::value<Context>* values)
+      : desc_(desc), values_(values) {}
+  basic_format_args(unsigned long long desc, const format_arg* args)
+      : desc_(desc), args_(args) {}
+
+ public:
+  basic_format_args() : desc_(0) {}
+
+  /**
+   \rst
+   Constructs a `basic_format_args` object from `~fmt::format_arg_store`.
+   \endrst
+   */
+  template <typename... Args>
+  FMT_INLINE basic_format_args(const format_arg_store<Context, Args...>& store)
+      : basic_format_args(store.desc, store.data_.args()) {}
+
+  /**
+   \rst
+   Constructs a `basic_format_args` object from
+   `~fmt::dynamic_format_arg_store`.
+   \endrst
+   */
+  FMT_INLINE basic_format_args(const dynamic_format_arg_store<Context>& store)
+      : basic_format_args(store.get_types(), store.data()) {}
+
+  /**
+   \rst
+   Constructs a `basic_format_args` object from a dynamic set of arguments.
+   \endrst
+   */
+  basic_format_args(const format_arg* args, int count)
+      : basic_format_args(detail::is_unpacked_bit | detail::to_unsigned(count),
+                          args) {}
+
+  /** Returns the argument with the specified id. */
+  format_arg get(int id) const {
+    format_arg arg;
+    if (!is_packed()) {
+      if (id < max_size()) arg = args_[id];
+      return arg;
+    }
+    if (id >= detail::max_packed_args) return arg;
+    arg.type_ = type(id);
+    if (arg.type_ == detail::type::none_type) return arg;
+    arg.value_ = values_[id];
+    return arg;
+  }
+
+  template <typename Char> format_arg get(basic_string_view<Char> name) const {
+    int id = get_id(name);
+    return id >= 0 ? get(id) : format_arg();
+  }
+
+  template <typename Char> int get_id(basic_string_view<Char> name) const {
+    if (!has_named_args()) return -1;
+    const auto& named_args =
+        (is_packed() ? values_[-1] : args_[-1].value_).named_args;
+    for (size_t i = 0; i < named_args.size; ++i) {
+      if (named_args.data[i].name == name) return named_args.data[i].id;
+    }
+    return -1;
+  }
+
+  int max_size() const {
+    unsigned long long max_packed = detail::max_packed_args;
+    return static_cast<int>(is_packed() ? max_packed
+                                        : desc_ & ~detail::is_unpacked_bit);
+  }
+};
+
+/** An alias to ``basic_format_args<context>``. */
+// It is a separate type rather than an alias to make symbols readable.
+struct format_args : basic_format_args<format_context> {
+  template <typename... Args>
+  FMT_INLINE format_args(const Args&... args) : basic_format_args(args...) {}
+};
+struct wformat_args : basic_format_args<wformat_context> {
+  using basic_format_args::basic_format_args;
+};
+
+namespace detail {
+
+// Reports a compile-time error if S is not a valid format string.
+template <typename..., typename S, FMT_ENABLE_IF(!is_compile_string<S>::value)>
+FMT_INLINE void check_format_string(const S&) {
+#ifdef FMT_ENFORCE_COMPILE_STRING
+  static_assert(is_compile_string<S>::value,
+                "FMT_ENFORCE_COMPILE_STRING requires all format strings to use "
+                "FMT_STRING.");
+#endif
+}
+template <typename..., typename S, FMT_ENABLE_IF(is_compile_string<S>::value)>
+void check_format_string(S);
+
+template <typename... Args, typename S, typename Char = char_t<S>>
+inline format_arg_store<buffer_context<Char>, remove_reference_t<Args>...>
+make_args_checked(const S& format_str,
+                  const remove_reference_t<Args>&... args) {
+  static_assert(count<(std::is_base_of<view, remove_reference_t<Args>>::value &&
+                       std::is_reference<Args>::value)...>() == 0,
+                "passing views as lvalues is disallowed");
+  check_format_string<Args...>(format_str);
+  return {args...};
+}
+
+template <typename Char, FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
+std::basic_string<Char> vformat(
+    basic_string_view<Char> format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args);
+
+FMT_API std::string vformat(string_view format_str, format_args args);
+
+template <typename Char>
+typename FMT_BUFFER_CONTEXT(Char)::iterator vformat_to(
+    buffer<Char>& buf, basic_string_view<Char> format_str,
+    basic_format_args<FMT_BUFFER_CONTEXT(type_identity_t<Char>)> args);
+
+template <typename Char, typename Args,
+          FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
+inline void vprint_mojibake(std::FILE*, basic_string_view<Char>, const Args&) {}
+
+FMT_API void vprint_mojibake(std::FILE*, string_view, format_args);
+#ifndef _WIN32
+inline void vprint_mojibake(std::FILE*, string_view, format_args) {}
+#endif
+}  // namespace detail
+
+/** Formats a string and writes the output to ``out``. */
+// GCC 8 and earlier cannot handle std::back_insert_iterator<Container> with
+// vformat_to<ArgFormatter>(...) overload, so SFINAE on iterator type instead.
+template <
+    typename OutputIt, typename S, typename Char = char_t<S>,
+    FMT_ENABLE_IF(detail::is_contiguous_back_insert_iterator<OutputIt>::value)>
+OutputIt vformat_to(
+    OutputIt out, const S& format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+  auto& c = detail::get_container(out);
+  detail::container_buffer<remove_reference_t<decltype(c)>> buf(c);
+  detail::vformat_to(buf, to_string_view(format_str), args);
+  return out;
+}
+
+template <typename Container, typename S, typename... Args,
+          FMT_ENABLE_IF(
+              is_contiguous<Container>::value&& detail::is_string<S>::value)>
+inline std::back_insert_iterator<Container> format_to(
+    std::back_insert_iterator<Container> out, const S& format_str,
+    Args&&... args) {
+  return vformat_to(out, to_string_view(format_str),
+                    detail::make_args_checked<Args...>(format_str, args...));
+}
+
+template <typename S, typename Char = char_t<S>>
+FMT_INLINE std::basic_string<Char> vformat(
+    const S& format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+  return detail::vformat(to_string_view(format_str), args);
+}
+
+/**
+  \rst
+  Formats arguments and returns the result as a string.
+
+  **Example**::
+
+    #include <fmt/core.h>
+    std::string message = fmt::format("The answer is {}", 42);
+  \endrst
+*/
+// Pass char_t as a default template parameter instead of using
+// std::basic_string<char_t<S>> to reduce the symbol size.
+template <typename S, typename... Args, typename Char = char_t<S>>
+FMT_INLINE std::basic_string<Char> format(const S& format_str, Args&&... args) {
+  const auto& vargs = detail::make_args_checked<Args...>(format_str, args...);
+  return detail::vformat(to_string_view(format_str), vargs);
+}
+
+FMT_API void vprint(string_view, format_args);
+FMT_API void vprint(std::FILE*, string_view, format_args);
+
+/**
+  \rst
+  Formats ``args`` according to specifications in ``format_str`` and writes the
+  output to the file ``f``. Strings are assumed to be Unicode-encoded unless the
+  ``FMT_UNICODE`` macro is set to 0.
+
+  **Example**::
+
+    fmt::print(stderr, "Don't {}!", "panic");
+  \endrst
+ */
+template <typename S, typename... Args, typename Char = char_t<S>>
+inline void print(std::FILE* f, const S& format_str, Args&&... args) {
+  const auto& vargs = detail::make_args_checked<Args...>(format_str, args...);
+  return detail::is_unicode<Char>()
+             ? vprint(f, to_string_view(format_str), vargs)
+             : detail::vprint_mojibake(f, to_string_view(format_str), vargs);
+}
+
+/**
+  \rst
+  Formats ``args`` according to specifications in ``format_str`` and writes
+  the output to ``stdout``. Strings are assumed to be Unicode-encoded unless
+  the ``FMT_UNICODE`` macro is set to 0.
+
+  **Example**::
+
+    fmt::print("Elapsed time: {0:.2f} seconds", 1.23);
+  \endrst
+ */
+template <typename S, typename... Args, typename Char = char_t<S>>
+inline void print(const S& format_str, Args&&... args) {
+  const auto& vargs = detail::make_args_checked<Args...>(format_str, args...);
+  return detail::is_unicode<Char>()
+             ? vprint(to_string_view(format_str), vargs)
+             : detail::vprint_mojibake(stdout, to_string_view(format_str),
+                                       vargs);
+}
+FMT_END_NAMESPACE
+
+#endif  // FMT_CORE_H_
diff --git a/external/fmtlib/include/fmt/format-inl.h b/external/fmtlib/include/fmt/format-inl.h
new file mode 100644
index 000000000..d8c9c8a5e
--- /dev/null
+++ b/external/fmtlib/include/fmt/format-inl.h
@@ -0,0 +1,1453 @@
+// Formatting library for C++ - implementation
+//
+// Copyright (c) 2012 - 2016, Victor Zverovich
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+#ifndef FMT_FORMAT_INL_H_
+#define FMT_FORMAT_INL_H_
+
+#include <cassert>
+#include <cctype>
+#include <climits>
+#include <cmath>
+#include <cstdarg>
+#include <cstring>  // for std::memmove
+#include <cwchar>
+#include <exception>
+
+#include "format.h"
+#if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
+#  include <locale>
+#endif
+
+#ifdef _WIN32
+#  if !defined(NOMINMAX) && !defined(WIN32_LEAN_AND_MEAN)
+#    define NOMINMAX
+#    define WIN32_LEAN_AND_MEAN
+#    include <windows.h>
+#    undef WIN32_LEAN_AND_MEAN
+#    undef NOMINMAX
+#  else
+#    include <windows.h>
+#  endif
+#  include <io.h>
+#endif
+
+#ifdef _MSC_VER
+#  pragma warning(push)
+#  pragma warning(disable : 4702)  // unreachable code
+#endif
+
+// Dummy implementations of strerror_r and strerror_s called if corresponding
+// system functions are not available.
+inline fmt::detail::null<> strerror_r(int, char*, ...) { return {}; }
+inline fmt::detail::null<> strerror_s(char*, size_t, ...) { return {}; }
+
+FMT_BEGIN_NAMESPACE
+namespace detail {
+
+FMT_FUNC void assert_fail(const char* file, int line, const char* message) {
+  // Use unchecked std::fprintf to avoid triggering another assertion when
+  // writing to stderr fails
+  std::fprintf(stderr, "%s:%d: assertion failed: %s", file, line, message);
+  // Chosen instead of std::abort to satisfy Clang in CUDA mode during device
+  // code pass.
+  std::terminate();
+}
+
+#ifndef _MSC_VER
+#  define FMT_SNPRINTF snprintf
+#else  // _MSC_VER
+inline int fmt_snprintf(char* buffer, size_t size, const char* format, ...) {
+  va_list args;
+  va_start(args, format);
+  int result = vsnprintf_s(buffer, size, _TRUNCATE, format, args);
+  va_end(args);
+  return result;
+}
+#  define FMT_SNPRINTF fmt_snprintf
+#endif  // _MSC_VER
+
+// A portable thread-safe version of strerror.
+// Sets buffer to point to a string describing the error code.
+// This can be either a pointer to a string stored in buffer,
+// or a pointer to some static immutable string.
+// Returns one of the following values:
+//   0      - success
+//   ERANGE - buffer is not large enough to store the error message
+//   other  - failure
+// Buffer should be at least of size 1.
+FMT_FUNC int safe_strerror(int error_code, char*& buffer,
+                           size_t buffer_size) FMT_NOEXCEPT {
+  FMT_ASSERT(buffer != nullptr && buffer_size != 0, "invalid buffer");
+
+  class dispatcher {
+   private:
+    int error_code_;
+    char*& buffer_;
+    size_t buffer_size_;
+
+    // A noop assignment operator to avoid bogus warnings.
+    void operator=(const dispatcher&) {}
+
+    // Handle the result of XSI-compliant version of strerror_r.
+    int handle(int result) {
+      // glibc versions before 2.13 return result in errno.
+      return result == -1 ? errno : result;
+    }
+
+    // Handle the result of GNU-specific version of strerror_r.
+    FMT_MAYBE_UNUSED
+    int handle(char* message) {
+      // If the buffer is full then the message is probably truncated.
+      if (message == buffer_ && strlen(buffer_) == buffer_size_ - 1)
+        return ERANGE;
+      buffer_ = message;
+      return 0;
+    }
+
+    // Handle the case when strerror_r is not available.
+    FMT_MAYBE_UNUSED
+    int handle(detail::null<>) {
+      return fallback(strerror_s(buffer_, buffer_size_, error_code_));
+    }
+
+    // Fallback to strerror_s when strerror_r is not available.
+    FMT_MAYBE_UNUSED
+    int fallback(int result) {
+      // If the buffer is full then the message is probably truncated.
+      return result == 0 && strlen(buffer_) == buffer_size_ - 1 ? ERANGE
+                                                                : result;
+    }
+
+#if !FMT_MSC_VER
+    // Fallback to strerror if strerror_r and strerror_s are not available.
+    int fallback(detail::null<>) {
+      errno = 0;
+      buffer_ = strerror(error_code_);
+      return errno;
+    }
+#endif
+
+   public:
+    dispatcher(int err_code, char*& buf, size_t buf_size)
+        : error_code_(err_code), buffer_(buf), buffer_size_(buf_size) {}
+
+    int run() { return handle(strerror_r(error_code_, buffer_, buffer_size_)); }
+  };
+  return dispatcher(error_code, buffer, buffer_size).run();
+}
+
+FMT_FUNC void format_error_code(detail::buffer<char>& out, int error_code,
+                                string_view message) FMT_NOEXCEPT {
+  // Report error code making sure that the output fits into
+  // inline_buffer_size to avoid dynamic memory allocation and potential
+  // bad_alloc.
+  out.resize(0);
+  static const char SEP[] = ": ";
+  static const char ERROR_STR[] = "error ";
+  // Subtract 2 to account for terminating null characters in SEP and ERROR_STR.
+  size_t error_code_size = sizeof(SEP) + sizeof(ERROR_STR) - 2;
+  auto abs_value = static_cast<uint32_or_64_or_128_t<int>>(error_code);
+  if (detail::is_negative(error_code)) {
+    abs_value = 0 - abs_value;
+    ++error_code_size;
+  }
+  error_code_size += detail::to_unsigned(detail::count_digits(abs_value));
+  auto it = std::back_inserter(out);
+  if (message.size() <= inline_buffer_size - error_code_size)
+    format_to(it, "{}{}", message, SEP);
+  format_to(it, "{}{}", ERROR_STR, error_code);
+  assert(out.size() <= inline_buffer_size);
+}
+
+FMT_FUNC void report_error(format_func func, int error_code,
+                           string_view message) FMT_NOEXCEPT {
+  memory_buffer full_message;
+  func(full_message, error_code, message);
+  // Don't use fwrite_fully because the latter may throw.
+  (void)std::fwrite(full_message.data(), full_message.size(), 1, stderr);
+  std::fputc('\n', stderr);
+}
+
+// A wrapper around fwrite that throws on error.
+FMT_FUNC void fwrite_fully(const void* ptr, size_t size, size_t count,
+                           FILE* stream) {
+  size_t written = std::fwrite(ptr, size, count, stream);
+  if (written < count) FMT_THROW(system_error(errno, "cannot write to file"));
+}
+}  // namespace detail
+
+#if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
+namespace detail {
+
+template <typename Locale>
+locale_ref::locale_ref(const Locale& loc) : locale_(&loc) {
+  static_assert(std::is_same<Locale, std::locale>::value, "");
+}
+
+template <typename Locale> Locale locale_ref::get() const {
+  static_assert(std::is_same<Locale, std::locale>::value, "");
+  return locale_ ? *static_cast<const std::locale*>(locale_) : std::locale();
+}
+
+template <typename Char> FMT_FUNC std::string grouping_impl(locale_ref loc) {
+  return std::use_facet<std::numpunct<Char>>(loc.get<std::locale>()).grouping();
+}
+template <typename Char> FMT_FUNC Char thousands_sep_impl(locale_ref loc) {
+  return std::use_facet<std::numpunct<Char>>(loc.get<std::locale>())
+      .thousands_sep();
+}
+template <typename Char> FMT_FUNC Char decimal_point_impl(locale_ref loc) {
+  return std::use_facet<std::numpunct<Char>>(loc.get<std::locale>())
+      .decimal_point();
+}
+}  // namespace detail
+#else
+template <typename Char>
+FMT_FUNC std::string detail::grouping_impl(locale_ref) {
+  return "\03";
+}
+template <typename Char> FMT_FUNC Char detail::thousands_sep_impl(locale_ref) {
+  return FMT_STATIC_THOUSANDS_SEPARATOR;
+}
+template <typename Char> FMT_FUNC Char detail::decimal_point_impl(locale_ref) {
+  return '.';
+}
+#endif
+
+FMT_API FMT_FUNC format_error::~format_error() FMT_NOEXCEPT = default;
+FMT_API FMT_FUNC system_error::~system_error() FMT_NOEXCEPT = default;
+
+FMT_FUNC void system_error::init(int err_code, string_view format_str,
+                                 format_args args) {
+  error_code_ = err_code;
+  memory_buffer buffer;
+  format_system_error(buffer, err_code, vformat(format_str, args));
+  std::runtime_error& base = *this;
+  base = std::runtime_error(to_string(buffer));
+}
+
+namespace detail {
+
+template <> FMT_FUNC int count_digits<4>(detail::fallback_uintptr n) {
+  // fallback_uintptr is always stored in little endian.
+  int i = static_cast<int>(sizeof(void*)) - 1;
+  while (i > 0 && n.value[i] == 0) --i;
+  auto char_digits = std::numeric_limits<unsigned char>::digits / 4;
+  return i >= 0 ? i * char_digits + count_digits<4, unsigned>(n.value[i]) : 1;
+}
+
+template <typename T>
+const typename basic_data<T>::digit_pair basic_data<T>::digits[] = {
+    {'0', '0'},  {'0', '1'},  {'0', '2'},  {'0', '3'},  {'0', '4'},
+    {'0', '5'},  {'0', '6'},  {'0', '7'},  {'0', '8'},  {'0', '9'},
+    {'1', '0'},  {'1', '1'},  {'1', '2'},  {'1', '3'},  {'1', '4'},
+    {'1', '5'},  {'1', '6'},  {'1', '7'},  {'1', '8'},  {'1', '9'},
+    {'2', '0'},  {'2', '1'},  {'2', '2'},  {'2', '3'},  {'2', '4'},
+    {'2', '5'},  {'2', '6'},  {'2', '7'},  {'2', '8'},  {'2', '9'},
+    {'3', '0'},  {'3', '1'},  {'3', '2'},  {'3', '3'},  {'3', '4'},
+    {'3', '5'},  {'3', '6'},  {'3', '7'},  {'3', '8'},  {'3', '9'},
+    {'4', '0'},  {'4', '1'},  {'4', '2'},  {'4', '3'},  {'4', '4'},
+    {'4', '5'},  {'4', '6'},  {'4', '7'},  {'4', '8'},  {'4', '9'},
+    {'5', '0'},  {'5', '1'},  {'5', '2'},  {'5', '3'},  {'5', '4'},
+    {'5', '5'},  {'5', '6'},  {'5', '7'},  {'5', '8'},  {'5', '9'},
+    {'6', '0'},  {'6', '1'},  {'6', '2'},  {'6', '3'},  {'6', '4'},
+    {'6', '5'},  {'6', '6'},  {'6', '7'},  {'6', '8'},  {'6', '9'},
+    {'7', '0'},  {'7', '1'},  {'7', '2'},  {'7', '3'},  {'7', '4'},
+    {'7', '5'},  {'7', '6'},  {'7', '7'},  {'7', '8'},  {'7', '9'},
+    {'8', '0'},  {'8', '1'},  {'8', '2'},  {'8', '3'},  {'8', '4'},
+    {'8', '5'},  {'8', '6'},  {'8', '7'},  {'8', '8'},  {'8', '9'},
+    {'9', '0'},  {'9', '1'},  {'9', '2'},  {'9', '3'},  {'9', '4'},
+    {'9', '5'},  {'9', '6'},  {'9', '7'},  {'9', '8'},  {'9', '9'}};
+
+template <typename T>
+const char basic_data<T>::hex_digits[] = "0123456789abcdef";
+
+#define FMT_POWERS_OF_10(factor)                                             \
+  factor * 10, (factor)*100, (factor)*1000, (factor)*10000, (factor)*100000, \
+      (factor)*1000000, (factor)*10000000, (factor)*100000000,               \
+      (factor)*1000000000
+
+template <typename T>
+const uint64_t basic_data<T>::powers_of_10_64[] = {
+    1, FMT_POWERS_OF_10(1), FMT_POWERS_OF_10(1000000000ULL),
+    10000000000000000000ULL};
+
+template <typename T>
+const uint32_t basic_data<T>::zero_or_powers_of_10_32[] = {0,
+                                                           FMT_POWERS_OF_10(1)};
+
+template <typename T>
+const uint64_t basic_data<T>::zero_or_powers_of_10_64[] = {
+    0, FMT_POWERS_OF_10(1), FMT_POWERS_OF_10(1000000000ULL),
+    10000000000000000000ULL};
+
+// Normalized 64-bit significands of pow(10, k), for k = -348, -340, ..., 340.
+// These are generated by support/compute-powers.py.
+template <typename T>
+const uint64_t basic_data<T>::pow10_significands[] = {
+    0xfa8fd5a0081c0288, 0xbaaee17fa23ebf76, 0x8b16fb203055ac76,
+    0xcf42894a5dce35ea, 0x9a6bb0aa55653b2d, 0xe61acf033d1a45df,
+    0xab70fe17c79ac6ca, 0xff77b1fcbebcdc4f, 0xbe5691ef416bd60c,
+    0x8dd01fad907ffc3c, 0xd3515c2831559a83, 0x9d71ac8fada6c9b5,
+    0xea9c227723ee8bcb, 0xaecc49914078536d, 0x823c12795db6ce57,
+    0xc21094364dfb5637, 0x9096ea6f3848984f, 0xd77485cb25823ac7,
+    0xa086cfcd97bf97f4, 0xef340a98172aace5, 0xb23867fb2a35b28e,
+    0x84c8d4dfd2c63f3b, 0xc5dd44271ad3cdba, 0x936b9fcebb25c996,
+    0xdbac6c247d62a584, 0xa3ab66580d5fdaf6, 0xf3e2f893dec3f126,
+    0xb5b5ada8aaff80b8, 0x87625f056c7c4a8b, 0xc9bcff6034c13053,
+    0x964e858c91ba2655, 0xdff9772470297ebd, 0xa6dfbd9fb8e5b88f,
+    0xf8a95fcf88747d94, 0xb94470938fa89bcf, 0x8a08f0f8bf0f156b,
+    0xcdb02555653131b6, 0x993fe2c6d07b7fac, 0xe45c10c42a2b3b06,
+    0xaa242499697392d3, 0xfd87b5f28300ca0e, 0xbce5086492111aeb,
+    0x8cbccc096f5088cc, 0xd1b71758e219652c, 0x9c40000000000000,
+    0xe8d4a51000000000, 0xad78ebc5ac620000, 0x813f3978f8940984,
+    0xc097ce7bc90715b3, 0x8f7e32ce7bea5c70, 0xd5d238a4abe98068,
+    0x9f4f2726179a2245, 0xed63a231d4c4fb27, 0xb0de65388cc8ada8,
+    0x83c7088e1aab65db, 0xc45d1df942711d9a, 0x924d692ca61be758,
+    0xda01ee641a708dea, 0xa26da3999aef774a, 0xf209787bb47d6b85,
+    0xb454e4a179dd1877, 0x865b86925b9bc5c2, 0xc83553c5c8965d3d,
+    0x952ab45cfa97a0b3, 0xde469fbd99a05fe3, 0xa59bc234db398c25,
+    0xf6c69a72a3989f5c, 0xb7dcbf5354e9bece, 0x88fcf317f22241e2,
+    0xcc20ce9bd35c78a5, 0x98165af37b2153df, 0xe2a0b5dc971f303a,
+    0xa8d9d1535ce3b396, 0xfb9b7cd9a4a7443c, 0xbb764c4ca7a44410,
+    0x8bab8eefb6409c1a, 0xd01fef10a657842c, 0x9b10a4e5e9913129,
+    0xe7109bfba19c0c9d, 0xac2820d9623bf429, 0x80444b5e7aa7cf85,
+    0xbf21e44003acdd2d, 0x8e679c2f5e44ff8f, 0xd433179d9c8cb841,
+    0x9e19db92b4e31ba9, 0xeb96bf6ebadf77d9, 0xaf87023b9bf0ee6b,
+};
+
+// Binary exponents of pow(10, k), for k = -348, -340, ..., 340, corresponding
+// to significands above.
+template <typename T>
+const int16_t basic_data<T>::pow10_exponents[] = {
+    -1220, -1193, -1166, -1140, -1113, -1087, -1060, -1034, -1007, -980, -954,
+    -927,  -901,  -874,  -847,  -821,  -794,  -768,  -741,  -715,  -688, -661,
+    -635,  -608,  -582,  -555,  -529,  -502,  -475,  -449,  -422,  -396, -369,
+    -343,  -316,  -289,  -263,  -236,  -210,  -183,  -157,  -130,  -103, -77,
+    -50,   -24,   3,     30,    56,    83,    109,   136,   162,   189,  216,
+    242,   269,   295,   322,   348,   375,   402,   428,   455,   481,  508,
+    534,   561,   588,   614,   641,   667,   694,   720,   747,   774,  800,
+    827,   853,   880,   907,   933,   960,   986,   1013,  1039,  1066};
+
+template <typename T>
+const char basic_data<T>::foreground_color[] = "\x1b[38;2;";
+template <typename T>
+const char basic_data<T>::background_color[] = "\x1b[48;2;";
+template <typename T> const char basic_data<T>::reset_color[] = "\x1b[0m";
+template <typename T> const wchar_t basic_data<T>::wreset_color[] = L"\x1b[0m";
+template <typename T> const char basic_data<T>::signs[] = {0, '-', '+', ' '};
+template <typename T>
+const char basic_data<T>::left_padding_shifts[] = {31, 31, 0, 1, 0};
+template <typename T>
+const char basic_data<T>::right_padding_shifts[] = {0, 31, 0, 1, 0};
+
+template <typename T> struct bits {
+  static FMT_CONSTEXPR_DECL const int value =
+      static_cast<int>(sizeof(T) * std::numeric_limits<unsigned char>::digits);
+};
+
+class fp;
+template <int SHIFT = 0> fp normalize(fp value);
+
+// Lower (upper) boundary is a value half way between a floating-point value
+// and its predecessor (successor). Boundaries have the same exponent as the
+// value so only significands are stored.
+struct boundaries {
+  uint64_t lower;
+  uint64_t upper;
+};
+
+// A handmade floating-point number f * pow(2, e).
+class fp {
+ private:
+  using significand_type = uint64_t;
+
+ public:
+  significand_type f;
+  int e;
+
+  // All sizes are in bits.
+  // Subtract 1 to account for an implicit most significant bit in the
+  // normalized form.
+  static FMT_CONSTEXPR_DECL const int double_significand_size =
+      std::numeric_limits<double>::digits - 1;
+  static FMT_CONSTEXPR_DECL const uint64_t implicit_bit =
+      1ULL << double_significand_size;
+  static FMT_CONSTEXPR_DECL const int significand_size =
+      bits<significand_type>::value;
+
+  fp() : f(0), e(0) {}
+  fp(uint64_t f_val, int e_val) : f(f_val), e(e_val) {}
+
+  // Constructs fp from an IEEE754 double. It is a template to prevent compile
+  // errors on platforms where double is not IEEE754.
+  template <typename Double> explicit fp(Double d) { assign(d); }
+
+  // Assigns d to this and return true iff predecessor is closer than successor.
+  template <typename Double, FMT_ENABLE_IF(sizeof(Double) == sizeof(uint64_t))>
+  bool assign(Double d) {
+    // Assume double is in the format [sign][exponent][significand].
+    using limits = std::numeric_limits<Double>;
+    const int exponent_size =
+        bits<Double>::value - double_significand_size - 1;  // -1 for sign
+    const uint64_t significand_mask = implicit_bit - 1;
+    const uint64_t exponent_mask = (~0ULL >> 1) & ~significand_mask;
+    const int exponent_bias = (1 << exponent_size) - limits::max_exponent - 1;
+    auto u = bit_cast<uint64_t>(d);
+    f = u & significand_mask;
+    int biased_e =
+        static_cast<int>((u & exponent_mask) >> double_significand_size);
+    // Predecessor is closer if d is a normalized power of 2 (f == 0) other than
+    // the smallest normalized number (biased_e > 1).
+    bool is_predecessor_closer = f == 0 && biased_e > 1;
+    if (biased_e != 0)
+      f += implicit_bit;
+    else
+      biased_e = 1;  // Subnormals use biased exponent 1 (min exponent).
+    e = biased_e - exponent_bias - double_significand_size;
+    return is_predecessor_closer;
+  }
+
+  template <typename Double, FMT_ENABLE_IF(sizeof(Double) != sizeof(uint64_t))>
+  bool assign(Double) {
+    *this = fp();
+    return false;
+  }
+
+  // Assigns d to this together with computing lower and upper boundaries,
+  // where a boundary is a value half way between the number and its predecessor
+  // (lower) or successor (upper). The upper boundary is normalized and lower
+  // has the same exponent but may be not normalized.
+  template <typename Double> boundaries assign_with_boundaries(Double d) {
+    bool is_lower_closer = assign(d);
+    fp lower =
+        is_lower_closer ? fp((f << 2) - 1, e - 2) : fp((f << 1) - 1, e - 1);
+    // 1 in normalize accounts for the exponent shift above.
+    fp upper = normalize<1>(fp((f << 1) + 1, e - 1));
+    lower.f <<= lower.e - upper.e;
+    return boundaries{lower.f, upper.f};
+  }
+
+  template <typename Double> boundaries assign_float_with_boundaries(Double d) {
+    assign(d);
+    constexpr int min_normal_e = std::numeric_limits<float>::min_exponent -
+                                 std::numeric_limits<double>::digits;
+    significand_type half_ulp = 1 << (std::numeric_limits<double>::digits -
+                                      std::numeric_limits<float>::digits - 1);
+    if (min_normal_e > e) half_ulp <<= min_normal_e - e;
+    fp upper = normalize<0>(fp(f + half_ulp, e));
+    fp lower = fp(
+        f - (half_ulp >> ((f == implicit_bit && e > min_normal_e) ? 1 : 0)), e);
+    lower.f <<= lower.e - upper.e;
+    return boundaries{lower.f, upper.f};
+  }
+};
+
+// Normalizes the value converted from double and multiplied by (1 << SHIFT).
+template <int SHIFT> fp normalize(fp value) {
+  // Handle subnormals.
+  const auto shifted_implicit_bit = fp::implicit_bit << SHIFT;
+  while ((value.f & shifted_implicit_bit) == 0) {
+    value.f <<= 1;
+    --value.e;
+  }
+  // Subtract 1 to account for hidden bit.
+  const auto offset =
+      fp::significand_size - fp::double_significand_size - SHIFT - 1;
+  value.f <<= offset;
+  value.e -= offset;
+  return value;
+}
+
+inline bool operator==(fp x, fp y) { return x.f == y.f && x.e == y.e; }
+
+// Computes lhs * rhs / pow(2, 64) rounded to nearest with half-up tie breaking.
+inline uint64_t multiply(uint64_t lhs, uint64_t rhs) {
+#if FMT_USE_INT128
+  auto product = static_cast<__uint128_t>(lhs) * rhs;
+  auto f = static_cast<uint64_t>(product >> 64);
+  return (static_cast<uint64_t>(product) & (1ULL << 63)) != 0 ? f + 1 : f;
+#else
+  // Multiply 32-bit parts of significands.
+  uint64_t mask = (1ULL << 32) - 1;
+  uint64_t a = lhs >> 32, b = lhs & mask;
+  uint64_t c = rhs >> 32, d = rhs & mask;
+  uint64_t ac = a * c, bc = b * c, ad = a * d, bd = b * d;
+  // Compute mid 64-bit of result and round.
+  uint64_t mid = (bd >> 32) + (ad & mask) + (bc & mask) + (1U << 31);
+  return ac + (ad >> 32) + (bc >> 32) + (mid >> 32);
+#endif
+}
+
+inline fp operator*(fp x, fp y) { return {multiply(x.f, y.f), x.e + y.e + 64}; }
+
+// Returns a cached power of 10 `c_k = c_k.f * pow(2, c_k.e)` such that its
+// (binary) exponent satisfies `min_exponent <= c_k.e <= min_exponent + 28`.
+inline fp get_cached_power(int min_exponent, int& pow10_exponent) {
+  const int64_t one_over_log2_10 = 0x4d104d42;  // round(pow(2, 32) / log2(10))
+  int index = static_cast<int>(
+      ((min_exponent + fp::significand_size - 1) * one_over_log2_10 +
+       ((int64_t(1) << 32) - 1))  // ceil
+      >> 32                       // arithmetic shift
+  );
+  // Decimal exponent of the first (smallest) cached power of 10.
+  const int first_dec_exp = -348;
+  // Difference between 2 consecutive decimal exponents in cached powers of 10.
+  const int dec_exp_step = 8;
+  index = (index - first_dec_exp - 1) / dec_exp_step + 1;
+  pow10_exponent = first_dec_exp + index * dec_exp_step;
+  return {data::pow10_significands[index], data::pow10_exponents[index]};
+}
+
+// A simple accumulator to hold the sums of terms in bigint::square if uint128_t
+// is not available.
+struct accumulator {
+  uint64_t lower;
+  uint64_t upper;
+
+  accumulator() : lower(0), upper(0) {}
+  explicit operator uint32_t() const { return static_cast<uint32_t>(lower); }
+
+  void operator+=(uint64_t n) {
+    lower += n;
+    if (lower < n) ++upper;
+  }
+  void operator>>=(int shift) {
+    assert(shift == 32);
+    (void)shift;
+    lower = (upper << 32) | (lower >> 32);
+    upper >>= 32;
+  }
+};
+
+class bigint {
+ private:
+  // A bigint is stored as an array of bigits (big digits), with bigit at index
+  // 0 being the least significant one.
+  using bigit = uint32_t;
+  using double_bigit = uint64_t;
+  enum { bigits_capacity = 32 };
+  basic_memory_buffer<bigit, bigits_capacity> bigits_;
+  int exp_;
+
+  bigit operator[](int index) const { return bigits_[to_unsigned(index)]; }
+  bigit& operator[](int index) { return bigits_[to_unsigned(index)]; }
+
+  static FMT_CONSTEXPR_DECL const int bigit_bits = bits<bigit>::value;
+
+  friend struct formatter<bigint>;
+
+  void subtract_bigits(int index, bigit other, bigit& borrow) {
+    auto result = static_cast<double_bigit>((*this)[index]) - other - borrow;
+    (*this)[index] = static_cast<bigit>(result);
+    borrow = static_cast<bigit>(result >> (bigit_bits * 2 - 1));
+  }
+
+  void remove_leading_zeros() {
+    int num_bigits = static_cast<int>(bigits_.size()) - 1;
+    while (num_bigits > 0 && (*this)[num_bigits] == 0) --num_bigits;
+    bigits_.resize(to_unsigned(num_bigits + 1));
+  }
+
+  // Computes *this -= other assuming aligned bigints and *this >= other.
+  void subtract_aligned(const bigint& other) {
+    FMT_ASSERT(other.exp_ >= exp_, "unaligned bigints");
+    FMT_ASSERT(compare(*this, other) >= 0, "");
+    bigit borrow = 0;
+    int i = other.exp_ - exp_;
+    for (size_t j = 0, n = other.bigits_.size(); j != n; ++i, ++j) {
+      subtract_bigits(i, other.bigits_[j], borrow);
+    }
+    while (borrow > 0) subtract_bigits(i, 0, borrow);
+    remove_leading_zeros();
+  }
+
+  void multiply(uint32_t value) {
+    const double_bigit wide_value = value;
+    bigit carry = 0;
+    for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
+      double_bigit result = bigits_[i] * wide_value + carry;
+      bigits_[i] = static_cast<bigit>(result);
+      carry = static_cast<bigit>(result >> bigit_bits);
+    }
+    if (carry != 0) bigits_.push_back(carry);
+  }
+
+  void multiply(uint64_t value) {
+    const bigit mask = ~bigit(0);
+    const double_bigit lower = value & mask;
+    const double_bigit upper = value >> bigit_bits;
+    double_bigit carry = 0;
+    for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
+      double_bigit result = bigits_[i] * lower + (carry & mask);
+      carry =
+          bigits_[i] * upper + (result >> bigit_bits) + (carry >> bigit_bits);
+      bigits_[i] = static_cast<bigit>(result);
+    }
+    while (carry != 0) {
+      bigits_.push_back(carry & mask);
+      carry >>= bigit_bits;
+    }
+  }
+
+ public:
+  bigint() : exp_(0) {}
+  explicit bigint(uint64_t n) { assign(n); }
+  ~bigint() { assert(bigits_.capacity() <= bigits_capacity); }
+
+  bigint(const bigint&) = delete;
+  void operator=(const bigint&) = delete;
+
+  void assign(const bigint& other) {
+    auto size = other.bigits_.size();
+    bigits_.resize(size);
+    auto data = other.bigits_.data();
+    std::copy(data, data + size, make_checked(bigits_.data(), size));
+    exp_ = other.exp_;
+  }
+
+  void assign(uint64_t n) {
+    size_t num_bigits = 0;
+    do {
+      bigits_[num_bigits++] = n & ~bigit(0);
+      n >>= bigit_bits;
+    } while (n != 0);
+    bigits_.resize(num_bigits);
+    exp_ = 0;
+  }
+
+  int num_bigits() const { return static_cast<int>(bigits_.size()) + exp_; }
+
+  FMT_NOINLINE bigint& operator<<=(int shift) {
+    assert(shift >= 0);
+    exp_ += shift / bigit_bits;
+    shift %= bigit_bits;
+    if (shift == 0) return *this;
+    bigit carry = 0;
+    for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
+      bigit c = bigits_[i] >> (bigit_bits - shift);
+      bigits_[i] = (bigits_[i] << shift) + carry;
+      carry = c;
+    }
+    if (carry != 0) bigits_.push_back(carry);
+    return *this;
+  }
+
+  template <typename Int> bigint& operator*=(Int value) {
+    FMT_ASSERT(value > 0, "");
+    multiply(uint32_or_64_or_128_t<Int>(value));
+    return *this;
+  }
+
+  friend int compare(const bigint& lhs, const bigint& rhs) {
+    int num_lhs_bigits = lhs.num_bigits(), num_rhs_bigits = rhs.num_bigits();
+    if (num_lhs_bigits != num_rhs_bigits)
+      return num_lhs_bigits > num_rhs_bigits ? 1 : -1;
+    int i = static_cast<int>(lhs.bigits_.size()) - 1;
+    int j = static_cast<int>(rhs.bigits_.size()) - 1;
+    int end = i - j;
+    if (end < 0) end = 0;
+    for (; i >= end; --i, --j) {
+      bigit lhs_bigit = lhs[i], rhs_bigit = rhs[j];
+      if (lhs_bigit != rhs_bigit) return lhs_bigit > rhs_bigit ? 1 : -1;
+    }
+    if (i != j) return i > j ? 1 : -1;
+    return 0;
+  }
+
+  // Returns compare(lhs1 + lhs2, rhs).
+  friend int add_compare(const bigint& lhs1, const bigint& lhs2,
+                         const bigint& rhs) {
+    int max_lhs_bigits = (std::max)(lhs1.num_bigits(), lhs2.num_bigits());
+    int num_rhs_bigits = rhs.num_bigits();
+    if (max_lhs_bigits + 1 < num_rhs_bigits) return -1;
+    if (max_lhs_bigits > num_rhs_bigits) return 1;
+    auto get_bigit = [](const bigint& n, int i) -> bigit {
+      return i >= n.exp_ && i < n.num_bigits() ? n[i - n.exp_] : 0;
+    };
+    double_bigit borrow = 0;
+    int min_exp = (std::min)((std::min)(lhs1.exp_, lhs2.exp_), rhs.exp_);
+    for (int i = num_rhs_bigits - 1; i >= min_exp; --i) {
+      double_bigit sum =
+          static_cast<double_bigit>(get_bigit(lhs1, i)) + get_bigit(lhs2, i);
+      bigit rhs_bigit = get_bigit(rhs, i);
+      if (sum > rhs_bigit + borrow) return 1;
+      borrow = rhs_bigit + borrow - sum;
+      if (borrow > 1) return -1;
+      borrow <<= bigit_bits;
+    }
+    return borrow != 0 ? -1 : 0;
+  }
+
+  // Assigns pow(10, exp) to this bigint.
+  void assign_pow10(int exp) {
+    assert(exp >= 0);
+    if (exp == 0) return assign(1);
+    // Find the top bit.
+    int bitmask = 1;
+    while (exp >= bitmask) bitmask <<= 1;
+    bitmask >>= 1;
+    // pow(10, exp) = pow(5, exp) * pow(2, exp). First compute pow(5, exp) by
+    // repeated squaring and multiplication.
+    assign(5);
+    bitmask >>= 1;
+    while (bitmask != 0) {
+      square();
+      if ((exp & bitmask) != 0) *this *= 5;
+      bitmask >>= 1;
+    }
+    *this <<= exp;  // Multiply by pow(2, exp) by shifting.
+  }
+
+  void square() {
+    basic_memory_buffer<bigit, bigits_capacity> n(std::move(bigits_));
+    int num_bigits = static_cast<int>(bigits_.size());
+    int num_result_bigits = 2 * num_bigits;
+    bigits_.resize(to_unsigned(num_result_bigits));
+    using accumulator_t = conditional_t<FMT_USE_INT128, uint128_t, accumulator>;
+    auto sum = accumulator_t();
+    for (int bigit_index = 0; bigit_index < num_bigits; ++bigit_index) {
+      // Compute bigit at position bigit_index of the result by adding
+      // cross-product terms n[i] * n[j] such that i + j == bigit_index.
+      for (int i = 0, j = bigit_index; j >= 0; ++i, --j) {
+        // Most terms are multiplied twice which can be optimized in the future.
+        sum += static_cast<double_bigit>(n[i]) * n[j];
+      }
+      (*this)[bigit_index] = static_cast<bigit>(sum);
+      sum >>= bits<bigit>::value;  // Compute the carry.
+    }
+    // Do the same for the top half.
+    for (int bigit_index = num_bigits; bigit_index < num_result_bigits;
+         ++bigit_index) {
+      for (int j = num_bigits - 1, i = bigit_index - j; i < num_bigits;)
+        sum += static_cast<double_bigit>(n[i++]) * n[j--];
+      (*this)[bigit_index] = static_cast<bigit>(sum);
+      sum >>= bits<bigit>::value;
+    }
+    --num_result_bigits;
+    remove_leading_zeros();
+    exp_ *= 2;
+  }
+
+  // Divides this bignum by divisor, assigning the remainder to this and
+  // returning the quotient.
+  int divmod_assign(const bigint& divisor) {
+    FMT_ASSERT(this != &divisor, "");
+    if (compare(*this, divisor) < 0) return 0;
+    int num_bigits = static_cast<int>(bigits_.size());
+    FMT_ASSERT(divisor.bigits_[divisor.bigits_.size() - 1u] != 0, "");
+    int exp_difference = exp_ - divisor.exp_;
+    if (exp_difference > 0) {
+      // Align bigints by adding trailing zeros to simplify subtraction.
+      bigits_.resize(to_unsigned(num_bigits + exp_difference));
+      for (int i = num_bigits - 1, j = i + exp_difference; i >= 0; --i, --j)
+        bigits_[j] = bigits_[i];
+      std::uninitialized_fill_n(bigits_.data(), exp_difference, 0);
+      exp_ -= exp_difference;
+    }
+    int quotient = 0;
+    do {
+      subtract_aligned(divisor);
+      ++quotient;
+    } while (compare(*this, divisor) >= 0);
+    return quotient;
+  }
+};
+
+enum class round_direction { unknown, up, down };
+
+// Given the divisor (normally a power of 10), the remainder = v % divisor for
+// some number v and the error, returns whether v should be rounded up, down, or
+// whether the rounding direction can't be determined due to error.
+// error should be less than divisor / 2.
+inline round_direction get_round_direction(uint64_t divisor, uint64_t remainder,
+                                           uint64_t error) {
+  FMT_ASSERT(remainder < divisor, "");  // divisor - remainder won't overflow.
+  FMT_ASSERT(error < divisor, "");      // divisor - error won't overflow.
+  FMT_ASSERT(error < divisor - error, "");  // error * 2 won't overflow.
+  // Round down if (remainder + error) * 2 <= divisor.
+  if (remainder <= divisor - remainder && error * 2 <= divisor - remainder * 2)
+    return round_direction::down;
+  // Round up if (remainder - error) * 2 >= divisor.
+  if (remainder >= error &&
+      remainder - error >= divisor - (remainder - error)) {
+    return round_direction::up;
+  }
+  return round_direction::unknown;
+}
+
+namespace digits {
+enum result {
+  more,  // Generate more digits.
+  done,  // Done generating digits.
+  error  // Digit generation cancelled due to an error.
+};
+}
+
+// A version of count_digits optimized for grisu_gen_digits.
+inline int grisu_count_digits(uint32_t n) {
+  if (n < 10) return 1;
+  if (n < 100) return 2;
+  if (n < 1000) return 3;
+  if (n < 10000) return 4;
+  if (n < 100000) return 5;
+  if (n < 1000000) return 6;
+  if (n < 10000000) return 7;
+  if (n < 100000000) return 8;
+  if (n < 1000000000) return 9;
+  return 10;
+}
+
+// Generates output using the Grisu digit-gen algorithm.
+// error: the size of the region (lower, upper) outside of which numbers
+// definitely do not round to value (Delta in Grisu3).
+template <typename Handler>
+FMT_ALWAYS_INLINE digits::result grisu_gen_digits(fp value, uint64_t error,
+                                                  int& exp, Handler& handler) {
+  const fp one(1ULL << -value.e, value.e);
+  // The integral part of scaled value (p1 in Grisu) = value / one. It cannot be
+  // zero because it contains a product of two 64-bit numbers with MSB set (due
+  // to normalization) - 1, shifted right by at most 60 bits.
+  auto integral = static_cast<uint32_t>(value.f >> -one.e);
+  FMT_ASSERT(integral != 0, "");
+  FMT_ASSERT(integral == value.f >> -one.e, "");
+  // The fractional part of scaled value (p2 in Grisu) c = value % one.
+  uint64_t fractional = value.f & (one.f - 1);
+  exp = grisu_count_digits(integral);  // kappa in Grisu.
+  // Divide by 10 to prevent overflow.
+  auto result = handler.on_start(data::powers_of_10_64[exp - 1] << -one.e,
+                                 value.f / 10, error * 10, exp);
+  if (result != digits::more) return result;
+  // Generate digits for the integral part. This can produce up to 10 digits.
+  do {
+    uint32_t digit = 0;
+    auto divmod_integral = [&](uint32_t divisor) {
+      digit = integral / divisor;
+      integral %= divisor;
+    };
+    // This optimization by Milo Yip reduces the number of integer divisions by
+    // one per iteration.
+    switch (exp) {
+    case 10:
+      divmod_integral(1000000000);
+      break;
+    case 9:
+      divmod_integral(100000000);
+      break;
+    case 8:
+      divmod_integral(10000000);
+      break;
+    case 7:
+      divmod_integral(1000000);
+      break;
+    case 6:
+      divmod_integral(100000);
+      break;
+    case 5:
+      divmod_integral(10000);
+      break;
+    case 4:
+      divmod_integral(1000);
+      break;
+    case 3:
+      divmod_integral(100);
+      break;
+    case 2:
+      divmod_integral(10);
+      break;
+    case 1:
+      digit = integral;
+      integral = 0;
+      break;
+    default:
+      FMT_ASSERT(false, "invalid number of digits");
+    }
+    --exp;
+    uint64_t remainder =
+        (static_cast<uint64_t>(integral) << -one.e) + fractional;
+    result = handler.on_digit(static_cast<char>('0' + digit),
+                              data::powers_of_10_64[exp] << -one.e, remainder,
+                              error, exp, true);
+    if (result != digits::more) return result;
+  } while (exp > 0);
+  // Generate digits for the fractional part.
+  for (;;) {
+    fractional *= 10;
+    error *= 10;
+    char digit =
+        static_cast<char>('0' + static_cast<char>(fractional >> -one.e));
+    fractional &= one.f - 1;
+    --exp;
+    result = handler.on_digit(digit, one.f, fractional, error, exp, false);
+    if (result != digits::more) return result;
+  }
+}
+
+// The fixed precision digit handler.
+struct fixed_handler {
+  char* buf;
+  int size;
+  int precision;
+  int exp10;
+  bool fixed;
+
+  digits::result on_start(uint64_t divisor, uint64_t remainder, uint64_t error,
+                          int& exp) {
+    // Non-fixed formats require at least one digit and no precision adjustment.
+    if (!fixed) return digits::more;
+    // Adjust fixed precision by exponent because it is relative to decimal
+    // point.
+    precision += exp + exp10;
+    // Check if precision is satisfied just by leading zeros, e.g.
+    // format("{:.2f}", 0.001) gives "0.00" without generating any digits.
+    if (precision > 0) return digits::more;
+    if (precision < 0) return digits::done;
+    auto dir = get_round_direction(divisor, remainder, error);
+    if (dir == round_direction::unknown) return digits::error;
+    buf[size++] = dir == round_direction::up ? '1' : '0';
+    return digits::done;
+  }
+
+  digits::result on_digit(char digit, uint64_t divisor, uint64_t remainder,
+                          uint64_t error, int, bool integral) {
+    FMT_ASSERT(remainder < divisor, "");
+    buf[size++] = digit;
+    if (size < precision) return digits::more;
+    if (!integral) {
+      // Check if error * 2 < divisor with overflow prevention.
+      // The check is not needed for the integral part because error = 1
+      // and divisor > (1 << 32) there.
+      if (error >= divisor || error >= divisor - error) return digits::error;
+    } else {
+      FMT_ASSERT(error == 1 && divisor > 2, "");
+    }
+    auto dir = get_round_direction(divisor, remainder, error);
+    if (dir != round_direction::up)
+      return dir == round_direction::down ? digits::done : digits::error;
+    ++buf[size - 1];
+    for (int i = size - 1; i > 0 && buf[i] > '9'; --i) {
+      buf[i] = '0';
+      ++buf[i - 1];
+    }
+    if (buf[0] > '9') {
+      buf[0] = '1';
+      buf[size++] = '0';
+    }
+    return digits::done;
+  }
+};
+
+// The shortest representation digit handler.
+struct grisu_shortest_handler {
+  char* buf;
+  int size;
+  // Distance between scaled value and upper bound (wp_W in Grisu3).
+  uint64_t diff;
+
+  digits::result on_start(uint64_t, uint64_t, uint64_t, int&) {
+    return digits::more;
+  }
+
+  // Decrement the generated number approaching value from above.
+  void round(uint64_t d, uint64_t divisor, uint64_t& remainder,
+             uint64_t error) {
+    while (
+        remainder < d && error - remainder >= divisor &&
+        (remainder + divisor < d || d - remainder >= remainder + divisor - d)) {
+      --buf[size - 1];
+      remainder += divisor;
+    }
+  }
+
+  // Implements Grisu's round_weed.
+  digits::result on_digit(char digit, uint64_t divisor, uint64_t remainder,
+                          uint64_t error, int exp, bool integral) {
+    buf[size++] = digit;
+    if (remainder >= error) return digits::more;
+    uint64_t unit = integral ? 1 : data::powers_of_10_64[-exp];
+    uint64_t up = (diff - 1) * unit;  // wp_Wup
+    round(up, divisor, remainder, error);
+    uint64_t down = (diff + 1) * unit;  // wp_Wdown
+    if (remainder < down && error - remainder >= divisor &&
+        (remainder + divisor < down ||
+         down - remainder > remainder + divisor - down)) {
+      return digits::error;
+    }
+    return 2 * unit <= remainder && remainder <= error - 4 * unit
+               ? digits::done
+               : digits::error;
+  }
+};
+
+// Formats value using a variation of the Fixed-Precision Positive
+// Floating-Point Printout ((FPP)^2) algorithm by Steele & White:
+// https://fmt.dev/p372-steele.pdf.
+template <typename Double>
+void fallback_format(Double d, buffer<char>& buf, int& exp10) {
+  bigint numerator;    // 2 * R in (FPP)^2.
+  bigint denominator;  // 2 * S in (FPP)^2.
+  // lower and upper are differences between value and corresponding boundaries.
+  bigint lower;             // (M^- in (FPP)^2).
+  bigint upper_store;       // upper's value if different from lower.
+  bigint* upper = nullptr;  // (M^+ in (FPP)^2).
+  fp value;
+  // Shift numerator and denominator by an extra bit or two (if lower boundary
+  // is closer) to make lower and upper integers. This eliminates multiplication
+  // by 2 during later computations.
+  // TODO: handle float
+  int shift = value.assign(d) ? 2 : 1;
+  uint64_t significand = value.f << shift;
+  if (value.e >= 0) {
+    numerator.assign(significand);
+    numerator <<= value.e;
+    lower.assign(1);
+    lower <<= value.e;
+    if (shift != 1) {
+      upper_store.assign(1);
+      upper_store <<= value.e + 1;
+      upper = &upper_store;
+    }
+    denominator.assign_pow10(exp10);
+    denominator <<= 1;
+  } else if (exp10 < 0) {
+    numerator.assign_pow10(-exp10);
+    lower.assign(numerator);
+    if (shift != 1) {
+      upper_store.assign(numerator);
+      upper_store <<= 1;
+      upper = &upper_store;
+    }
+    numerator *= significand;
+    denominator.assign(1);
+    denominator <<= shift - value.e;
+  } else {
+    numerator.assign(significand);
+    denominator.assign_pow10(exp10);
+    denominator <<= shift - value.e;
+    lower.assign(1);
+    if (shift != 1) {
+      upper_store.assign(1ULL << 1);
+      upper = &upper_store;
+    }
+  }
+  if (!upper) upper = &lower;
+  // Invariant: value == (numerator / denominator) * pow(10, exp10).
+  bool even = (value.f & 1) == 0;
+  int num_digits = 0;
+  char* data = buf.data();
+  for (;;) {
+    int digit = numerator.divmod_assign(denominator);
+    bool low = compare(numerator, lower) - even < 0;  // numerator <[=] lower.
+    // numerator + upper >[=] pow10:
+    bool high = add_compare(numerator, *upper, denominator) + even > 0;
+    data[num_digits++] = static_cast<char>('0' + digit);
+    if (low || high) {
+      if (!low) {
+        ++data[num_digits - 1];
+      } else if (high) {
+        int result = add_compare(numerator, numerator, denominator);
+        // Round half to even.
+        if (result > 0 || (result == 0 && (digit % 2) != 0))
+          ++data[num_digits - 1];
+      }
+      buf.resize(to_unsigned(num_digits));
+      exp10 -= num_digits - 1;
+      return;
+    }
+    numerator *= 10;
+    lower *= 10;
+    if (upper != &lower) *upper *= 10;
+  }
+}
+
+// Formats value using the Grisu algorithm
+// (https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf)
+// if T is a IEEE754 binary32 or binary64 and snprintf otherwise.
+template <typename T>
+int format_float(T value, int precision, float_specs specs, buffer<char>& buf) {
+  static_assert(!std::is_same<T, float>::value, "");
+  FMT_ASSERT(value >= 0, "value is negative");
+
+  const bool fixed = specs.format == float_format::fixed;
+  if (value <= 0) {  // <= instead of == to silence a warning.
+    if (precision <= 0 || !fixed) {
+      buf.push_back('0');
+      return 0;
+    }
+    buf.resize(to_unsigned(precision));
+    std::uninitialized_fill_n(buf.data(), precision, '0');
+    return -precision;
+  }
+
+  if (!specs.use_grisu) return snprintf_float(value, precision, specs, buf);
+
+  int exp = 0;
+  const int min_exp = -60;  // alpha in Grisu.
+  int cached_exp10 = 0;     // K in Grisu.
+  if (precision < 0) {
+    fp fp_value;
+    auto boundaries = specs.binary32
+                          ? fp_value.assign_float_with_boundaries(value)
+                          : fp_value.assign_with_boundaries(value);
+    fp_value = normalize(fp_value);
+    // Find a cached power of 10 such that multiplying value by it will bring
+    // the exponent in the range [min_exp, -32].
+    const fp cached_pow = get_cached_power(
+        min_exp - (fp_value.e + fp::significand_size), cached_exp10);
+    // Multiply value and boundaries by the cached power of 10.
+    fp_value = fp_value * cached_pow;
+    boundaries.lower = multiply(boundaries.lower, cached_pow.f);
+    boundaries.upper = multiply(boundaries.upper, cached_pow.f);
+    assert(min_exp <= fp_value.e && fp_value.e <= -32);
+    --boundaries.lower;  // \tilde{M}^- - 1 ulp -> M^-_{\downarrow}.
+    ++boundaries.upper;  // \tilde{M}^+ + 1 ulp -> M^+_{\uparrow}.
+    // Numbers outside of (lower, upper) definitely do not round to value.
+    grisu_shortest_handler handler{buf.data(), 0,
+                                   boundaries.upper - fp_value.f};
+    auto result =
+        grisu_gen_digits(fp(boundaries.upper, fp_value.e),
+                         boundaries.upper - boundaries.lower, exp, handler);
+    if (result == digits::error) {
+      exp += handler.size - cached_exp10 - 1;
+      fallback_format(value, buf, exp);
+      return exp;
+    }
+    buf.resize(to_unsigned(handler.size));
+  } else {
+    if (precision > 17) return snprintf_float(value, precision, specs, buf);
+    fp normalized = normalize(fp(value));
+    const auto cached_pow = get_cached_power(
+        min_exp - (normalized.e + fp::significand_size), cached_exp10);
+    normalized = normalized * cached_pow;
+    fixed_handler handler{buf.data(), 0, precision, -cached_exp10, fixed};
+    if (grisu_gen_digits(normalized, 1, exp, handler) == digits::error)
+      return snprintf_float(value, precision, specs, buf);
+    int num_digits = handler.size;
+    if (!fixed) {
+      // Remove trailing zeros.
+      while (num_digits > 0 && buf[num_digits - 1] == '0') {
+        --num_digits;
+        ++exp;
+      }
+    }
+    buf.resize(to_unsigned(num_digits));
+  }
+  return exp - cached_exp10;
+}
+
+template <typename T>
+int snprintf_float(T value, int precision, float_specs specs,
+                   buffer<char>& buf) {
+  // Buffer capacity must be non-zero, otherwise MSVC's vsnprintf_s will fail.
+  FMT_ASSERT(buf.capacity() > buf.size(), "empty buffer");
+  static_assert(!std::is_same<T, float>::value, "");
+
+  // Subtract 1 to account for the difference in precision since we use %e for
+  // both general and exponent format.
+  if (specs.format == float_format::general ||
+      specs.format == float_format::exp)
+    precision = (precision >= 0 ? precision : 6) - 1;
+
+  // Build the format string.
+  enum { max_format_size = 7 };  // The longest format is "%#.*Le".
+  char format[max_format_size];
+  char* format_ptr = format;
+  *format_ptr++ = '%';
+  if (specs.showpoint && specs.format == float_format::hex) *format_ptr++ = '#';
+  if (precision >= 0) {
+    *format_ptr++ = '.';
+    *format_ptr++ = '*';
+  }
+  if (std::is_same<T, long double>()) *format_ptr++ = 'L';
+  *format_ptr++ = specs.format != float_format::hex
+                      ? (specs.format == float_format::fixed ? 'f' : 'e')
+                      : (specs.upper ? 'A' : 'a');
+  *format_ptr = '\0';
+
+  // Format using snprintf.
+  auto offset = buf.size();
+  for (;;) {
+    auto begin = buf.data() + offset;
+    auto capacity = buf.capacity() - offset;
+#ifdef FMT_FUZZ
+    if (precision > 100000)
+      throw std::runtime_error(
+          "fuzz mode - avoid large allocation inside snprintf");
+#endif
+    // Suppress the warning about a nonliteral format string.
+    // Cannot use auto because of a bug in MinGW (#1532).
+    int (*snprintf_ptr)(char*, size_t, const char*, ...) = FMT_SNPRINTF;
+    int result = precision >= 0
+                     ? snprintf_ptr(begin, capacity, format, precision, value)
+                     : snprintf_ptr(begin, capacity, format, value);
+    if (result < 0) {
+      buf.reserve(buf.capacity() + 1);  // The buffer will grow exponentially.
+      continue;
+    }
+    auto size = to_unsigned(result);
+    // Size equal to capacity means that the last character was truncated.
+    if (size >= capacity) {
+      buf.reserve(size + offset + 1);  // Add 1 for the terminating '\0'.
+      continue;
+    }
+    auto is_digit = [](char c) { return c >= '0' && c <= '9'; };
+    if (specs.format == float_format::fixed) {
+      if (precision == 0) {
+        buf.resize(size);
+        return 0;
+      }
+      // Find and remove the decimal point.
+      auto end = begin + size, p = end;
+      do {
+        --p;
+      } while (is_digit(*p));
+      int fraction_size = static_cast<int>(end - p - 1);
+      std::memmove(p, p + 1, to_unsigned(fraction_size));
+      buf.resize(size - 1);
+      return -fraction_size;
+    }
+    if (specs.format == float_format::hex) {
+      buf.resize(size + offset);
+      return 0;
+    }
+    // Find and parse the exponent.
+    auto end = begin + size, exp_pos = end;
+    do {
+      --exp_pos;
+    } while (*exp_pos != 'e');
+    char sign = exp_pos[1];
+    assert(sign == '+' || sign == '-');
+    int exp = 0;
+    auto p = exp_pos + 2;  // Skip 'e' and sign.
+    do {
+      assert(is_digit(*p));
+      exp = exp * 10 + (*p++ - '0');
+    } while (p != end);
+    if (sign == '-') exp = -exp;
+    int fraction_size = 0;
+    if (exp_pos != begin + 1) {
+      // Remove trailing zeros.
+      auto fraction_end = exp_pos - 1;
+      while (*fraction_end == '0') --fraction_end;
+      // Move the fractional part left to get rid of the decimal point.
+      fraction_size = static_cast<int>(fraction_end - begin - 1);
+      std::memmove(begin + 1, begin + 2, to_unsigned(fraction_size));
+    }
+    buf.resize(to_unsigned(fraction_size) + offset + 1);
+    return exp - fraction_size;
+  }
+}
+
+// A public domain branchless UTF-8 decoder by Christopher Wellons:
+// https://github.com/skeeto/branchless-utf8
+/* Decode the next character, c, from buf, reporting errors in e.
+ *
+ * Since this is a branchless decoder, four bytes will be read from the
+ * buffer regardless of the actual length of the next character. This
+ * means the buffer _must_ have at least three bytes of zero padding
+ * following the end of the data stream.
+ *
+ * Errors are reported in e, which will be non-zero if the parsed
+ * character was somehow invalid: invalid byte sequence, non-canonical
+ * encoding, or a surrogate half.
+ *
+ * The function returns a pointer to the next character. When an error
+ * occurs, this pointer will be a guess that depends on the particular
+ * error, but it will always advance at least one byte.
+ */
+FMT_FUNC const char* utf8_decode(const char* buf, uint32_t* c, int* e) {
+  static const char lengths[] = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+                                 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0,
+                                 0, 0, 2, 2, 2, 2, 3, 3, 4, 0};
+  static const int masks[] = {0x00, 0x7f, 0x1f, 0x0f, 0x07};
+  static const uint32_t mins[] = {4194304, 0, 128, 2048, 65536};
+  static const int shiftc[] = {0, 18, 12, 6, 0};
+  static const int shifte[] = {0, 6, 4, 2, 0};
+
+  auto s = reinterpret_cast<const unsigned char*>(buf);
+  int len = lengths[s[0] >> 3];
+
+  // Compute the pointer to the next character early so that the next
+  // iteration can start working on the next character. Neither Clang
+  // nor GCC figure out this reordering on their own.
+  const char* next = buf + len + !len;
+
+  // Assume a four-byte character and load four bytes. Unused bits are
+  // shifted out.
+  *c = uint32_t(s[0] & masks[len]) << 18;
+  *c |= uint32_t(s[1] & 0x3f) << 12;
+  *c |= uint32_t(s[2] & 0x3f) << 6;
+  *c |= uint32_t(s[3] & 0x3f) << 0;
+  *c >>= shiftc[len];
+
+  // Accumulate the various error conditions.
+  *e = (*c < mins[len]) << 6;       // non-canonical encoding
+  *e |= ((*c >> 11) == 0x1b) << 7;  // surrogate half?
+  *e |= (*c > 0x10FFFF) << 8;       // out of range?
+  *e |= (s[1] & 0xc0) >> 2;
+  *e |= (s[2] & 0xc0) >> 4;
+  *e |= (s[3]) >> 6;
+  *e ^= 0x2a;  // top two bits of each tail byte correct?
+  *e >>= shifte[len];
+
+  return next;
+}
+}  // namespace detail
+
+template <> struct formatter<detail::bigint> {
+  format_parse_context::iterator parse(format_parse_context& ctx) {
+    return ctx.begin();
+  }
+
+  format_context::iterator format(const detail::bigint& n,
+                                  format_context& ctx) {
+    auto out = ctx.out();
+    bool first = true;
+    for (auto i = n.bigits_.size(); i > 0; --i) {
+      auto value = n.bigits_[i - 1u];
+      if (first) {
+        out = format_to(out, "{:x}", value);
+        first = false;
+        continue;
+      }
+      out = format_to(out, "{:08x}", value);
+    }
+    if (n.exp_ > 0)
+      out = format_to(out, "p{}", n.exp_ * detail::bigint::bigit_bits);
+    return out;
+  }
+};
+
+FMT_FUNC detail::utf8_to_utf16::utf8_to_utf16(string_view s) {
+  auto transcode = [this](const char* p) {
+    auto cp = uint32_t();
+    auto error = 0;
+    p = utf8_decode(p, &cp, &error);
+    if (error != 0) FMT_THROW(std::runtime_error("invalid utf8"));
+    if (cp <= 0xFFFF) {
+      buffer_.push_back(static_cast<wchar_t>(cp));
+    } else {
+      cp -= 0x10000;
+      buffer_.push_back(static_cast<wchar_t>(0xD800 + (cp >> 10)));
+      buffer_.push_back(static_cast<wchar_t>(0xDC00 + (cp & 0x3FF)));
+    }
+    return p;
+  };
+  auto p = s.data();
+  const size_t block_size = 4;  // utf8_decode always reads blocks of 4 chars.
+  if (s.size() >= block_size) {
+    for (auto end = p + s.size() - block_size + 1; p < end;) p = transcode(p);
+  }
+  if (auto num_chars_left = s.data() + s.size() - p) {
+    char buf[2 * block_size - 1] = {};
+    memcpy(buf, p, to_unsigned(num_chars_left));
+    p = buf;
+    do {
+      p = transcode(p);
+    } while (p - buf < num_chars_left);
+  }
+  buffer_.push_back(0);
+}
+
+FMT_FUNC void format_system_error(detail::buffer<char>& out, int error_code,
+                                  string_view message) FMT_NOEXCEPT {
+  FMT_TRY {
+    memory_buffer buf;
+    buf.resize(inline_buffer_size);
+    for (;;) {
+      char* system_message = &buf[0];
+      int result =
+          detail::safe_strerror(error_code, system_message, buf.size());
+      if (result == 0) {
+        format_to(std::back_inserter(out), "{}: {}", message, system_message);
+        return;
+      }
+      if (result != ERANGE)
+        break;  // Can't get error message, report error code instead.
+      buf.resize(buf.size() * 2);
+    }
+  }
+  FMT_CATCH(...) {}
+  format_error_code(out, error_code, message);
+}
+
+FMT_FUNC void detail::error_handler::on_error(const char* message) {
+  FMT_THROW(format_error(message));
+}
+
+FMT_FUNC void report_system_error(int error_code,
+                                  fmt::string_view message) FMT_NOEXCEPT {
+  report_error(format_system_error, error_code, message);
+}
+
+struct stringifier {
+  template <typename T> FMT_INLINE std::string operator()(T value) const {
+    return to_string(value);
+  }
+  std::string operator()(basic_format_arg<format_context>::handle h) const {
+    memory_buffer buf;
+    detail::buffer<char>& base = buf;
+    format_parse_context parse_ctx({});
+    format_context format_ctx(std::back_inserter(base), {}, {});
+    h.format(parse_ctx, format_ctx);
+    return to_string(buf);
+  }
+};
+
+FMT_FUNC std::string detail::vformat(string_view format_str, format_args args) {
+  if (format_str.size() == 2 && equal2(format_str.data(), "{}")) {
+    auto arg = args.get(0);
+    if (!arg) error_handler().on_error("argument not found");
+    return visit_format_arg(stringifier(), arg);
+  }
+  memory_buffer buffer;
+  detail::vformat_to(buffer, format_str, args);
+  return to_string(buffer);
+}
+
+FMT_FUNC void vprint(std::FILE* f, string_view format_str, format_args args) {
+  memory_buffer buffer;
+  detail::vformat_to(buffer, format_str,
+                     basic_format_args<buffer_context<char>>(args));
+#ifdef _WIN32
+  auto fd = _fileno(f);
+  if (_isatty(fd)) {
+    detail::utf8_to_utf16 u16(string_view(buffer.data(), buffer.size()));
+    auto written = DWORD();
+    if (!WriteConsoleW(reinterpret_cast<HANDLE>(_get_osfhandle(fd)),
+                       u16.c_str(), static_cast<DWORD>(u16.size()), &written,
+                       nullptr)) {
+      FMT_THROW(format_error("failed to write to console"));
+    }
+    return;
+  }
+#endif
+  detail::fwrite_fully(buffer.data(), 1, buffer.size(), f);
+}
+
+#ifdef _WIN32
+// Print assuming legacy (non-Unicode) encoding.
+FMT_FUNC void detail::vprint_mojibake(std::FILE* f, string_view format_str,
+                                      format_args args) {
+  memory_buffer buffer;
+  detail::vformat_to(buffer, format_str,
+                     basic_format_args<buffer_context<char>>(args));
+  fwrite_fully(buffer.data(), 1, buffer.size(), f);
+}
+#endif
+
+FMT_FUNC void vprint(string_view format_str, format_args args) {
+  vprint(stdout, format_str, args);
+}
+
+FMT_END_NAMESPACE
+
+#ifdef _MSC_VER
+#  pragma warning(pop)
+#endif
+
+#endif  // FMT_FORMAT_INL_H_
diff --git a/external/fmtlib/include/fmt/format.h b/external/fmtlib/include/fmt/format.h
new file mode 100644
index 000000000..17509b7b4
--- /dev/null
+++ b/external/fmtlib/include/fmt/format.h
@@ -0,0 +1,3729 @@
+/*
+ Formatting library for C++
+
+ Copyright (c) 2012 - present, Victor Zverovich
+
+ Permission is hereby granted, free of charge, to any person obtaining
+ a copy of this software and associated documentation files (the
+ "Software"), to deal in the Software without restriction, including
+ without limitation the rights to use, copy, modify, merge, publish,
+ distribute, sublicense, and/or sell copies of the Software, and to
+ permit persons to whom the Software is furnished to do so, subject to
+ the following conditions:
+
+ The above copyright notice and this permission notice shall be
+ included in all copies or substantial portions of the Software.
+
+ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+ --- Optional exception to the license ---
+
+ As an exception, if, as a result of your compiling your source code, portions
+ of this Software are embedded into a machine-executable object form of such
+ source code, you may redistribute such embedded portions in such object form
+ without including the above copyright and permission notices.
+ */
+
+#ifndef FMT_FORMAT_H_
+#define FMT_FORMAT_H_
+
+#include <algorithm>
+#include <cerrno>
+#include <cmath>
+#include <cstdint>
+#include <limits>
+#include <memory>
+#include <stdexcept>
+
+#include "core.h"
+
+#ifdef __INTEL_COMPILER
+#  define FMT_ICC_VERSION __INTEL_COMPILER
+#elif defined(__ICL)
+#  define FMT_ICC_VERSION __ICL
+#else
+#  define FMT_ICC_VERSION 0
+#endif
+
+#ifdef __NVCC__
+#  define FMT_CUDA_VERSION (__CUDACC_VER_MAJOR__ * 100 + __CUDACC_VER_MINOR__)
+#else
+#  define FMT_CUDA_VERSION 0
+#endif
+
+#ifdef __has_builtin
+#  define FMT_HAS_BUILTIN(x) __has_builtin(x)
+#else
+#  define FMT_HAS_BUILTIN(x) 0
+#endif
+
+#if FMT_GCC_VERSION || FMT_CLANG_VERSION
+#  define FMT_NOINLINE __attribute__((noinline))
+#else
+#  define FMT_NOINLINE
+#endif
+
+#if __cplusplus == 201103L || __cplusplus == 201402L
+#  if defined(__clang__)
+#    define FMT_FALLTHROUGH [[clang::fallthrough]]
+#  elif FMT_GCC_VERSION >= 700 && !defined(__PGI) && \
+      (!defined(__EDG_VERSION__) || __EDG_VERSION__ >= 520)
+#    define FMT_FALLTHROUGH [[gnu::fallthrough]]
+#  else
+#    define FMT_FALLTHROUGH
+#  endif
+#elif FMT_HAS_CPP17_ATTRIBUTE(fallthrough) || \
+    (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
+#  define FMT_FALLTHROUGH [[fallthrough]]
+#else
+#  define FMT_FALLTHROUGH
+#endif
+
+#ifndef FMT_MAYBE_UNUSED
+#  if FMT_HAS_CPP17_ATTRIBUTE(maybe_unused)
+#    define FMT_MAYBE_UNUSED [[maybe_unused]]
+#  else
+#    define FMT_MAYBE_UNUSED
+#  endif
+#endif
+
+#ifndef FMT_THROW
+#  if FMT_EXCEPTIONS
+#    if FMT_MSC_VER || FMT_NVCC
+FMT_BEGIN_NAMESPACE
+namespace detail {
+template <typename Exception> inline void do_throw(const Exception& x) {
+  // Silence unreachable code warnings in MSVC and NVCC because these
+  // are nearly impossible to fix in a generic code.
+  volatile bool b = true;
+  if (b) throw x;
+}
+}  // namespace detail
+FMT_END_NAMESPACE
+#      define FMT_THROW(x) detail::do_throw(x)
+#    else
+#      define FMT_THROW(x) throw x
+#    endif
+#  else
+#    define FMT_THROW(x)              \
+      do {                            \
+        static_cast<void>(sizeof(x)); \
+        FMT_ASSERT(false, "");        \
+      } while (false)
+#  endif
+#endif
+
+#if FMT_EXCEPTIONS
+#  define FMT_TRY try
+#  define FMT_CATCH(x) catch (x)
+#else
+#  define FMT_TRY if (true)
+#  define FMT_CATCH(x) if (false)
+#endif
+
+#ifndef FMT_USE_USER_DEFINED_LITERALS
+// EDG based compilers (Intel, NVIDIA, Elbrus, etc), GCC and MSVC support UDLs.
+#  if (FMT_HAS_FEATURE(cxx_user_literals) || FMT_GCC_VERSION >= 407 || \
+       FMT_MSC_VER >= 1900) &&                                         \
+      (!defined(__EDG_VERSION__) || __EDG_VERSION__ >= /* UDL feature */ 480)
+#    define FMT_USE_USER_DEFINED_LITERALS 1
+#  else
+#    define FMT_USE_USER_DEFINED_LITERALS 0
+#  endif
+#endif
+
+#ifndef FMT_USE_UDL_TEMPLATE
+// EDG frontend based compilers (icc, nvcc, etc) and GCC < 6.4 do not properly
+// support UDL templates and GCC >= 9 warns about them.
+#  if FMT_USE_USER_DEFINED_LITERALS &&                         \
+      (!defined(__EDG_VERSION__) || __EDG_VERSION__ >= 501) && \
+      ((FMT_GCC_VERSION >= 604 && __cplusplus >= 201402L) ||   \
+       FMT_CLANG_VERSION >= 304)
+#    define FMT_USE_UDL_TEMPLATE 1
+#  else
+#    define FMT_USE_UDL_TEMPLATE 0
+#  endif
+#endif
+
+#ifndef FMT_USE_FLOAT
+#  define FMT_USE_FLOAT 1
+#endif
+
+#ifndef FMT_USE_DOUBLE
+#  define FMT_USE_DOUBLE 1
+#endif
+
+#ifndef FMT_USE_LONG_DOUBLE
+#  define FMT_USE_LONG_DOUBLE 1
+#endif
+
+// __builtin_clz is broken in clang with Microsoft CodeGen:
+// https://github.com/fmtlib/fmt/issues/519
+#if (FMT_GCC_VERSION || FMT_HAS_BUILTIN(__builtin_clz)) && !FMT_MSC_VER
+#  define FMT_BUILTIN_CLZ(n) __builtin_clz(n)
+#endif
+#if (FMT_GCC_VERSION || FMT_HAS_BUILTIN(__builtin_clzll)) && !FMT_MSC_VER
+#  define FMT_BUILTIN_CLZLL(n) __builtin_clzll(n)
+#endif
+
+// Some compilers masquerade as both MSVC and GCC-likes or otherwise support
+// __builtin_clz and __builtin_clzll, so only define FMT_BUILTIN_CLZ using the
+// MSVC intrinsics if the clz and clzll builtins are not available.
+#if FMT_MSC_VER && !defined(FMT_BUILTIN_CLZLL) && !defined(_MANAGED)
+#  include <intrin.h>  // _BitScanReverse, _BitScanReverse64
+
+FMT_BEGIN_NAMESPACE
+namespace detail {
+// Avoid Clang with Microsoft CodeGen's -Wunknown-pragmas warning.
+#  ifndef __clang__
+#    pragma intrinsic(_BitScanReverse)
+#  endif
+inline uint32_t clz(uint32_t x) {
+  unsigned long r = 0;
+  _BitScanReverse(&r, x);
+
+  FMT_ASSERT(x != 0, "");
+  // Static analysis complains about using uninitialized data
+  // "r", but the only way that can happen is if "x" is 0,
+  // which the callers guarantee to not happen.
+  FMT_SUPPRESS_MSC_WARNING(6102)
+  return 31 - r;
+}
+#  define FMT_BUILTIN_CLZ(n) detail::clz(n)
+
+#  if defined(_WIN64) && !defined(__clang__)
+#    pragma intrinsic(_BitScanReverse64)
+#  endif
+
+inline uint32_t clzll(uint64_t x) {
+  unsigned long r = 0;
+#  ifdef _WIN64
+  _BitScanReverse64(&r, x);
+#  else
+  // Scan the high 32 bits.
+  if (_BitScanReverse(&r, static_cast<uint32_t>(x >> 32))) return 63 - (r + 32);
+
+  // Scan the low 32 bits.
+  _BitScanReverse(&r, static_cast<uint32_t>(x));
+#  endif
+
+  FMT_ASSERT(x != 0, "");
+  // Static analysis complains about using uninitialized data
+  // "r", but the only way that can happen is if "x" is 0,
+  // which the callers guarantee to not happen.
+  FMT_SUPPRESS_MSC_WARNING(6102)
+  return 63 - r;
+}
+#  define FMT_BUILTIN_CLZLL(n) detail::clzll(n)
+}  // namespace detail
+FMT_END_NAMESPACE
+#endif
+
+// Enable the deprecated numeric alignment.
+#ifndef FMT_DEPRECATED_NUMERIC_ALIGN
+#  define FMT_DEPRECATED_NUMERIC_ALIGN 0
+#endif
+
+FMT_BEGIN_NAMESPACE
+namespace detail {
+
+// An equivalent of `*reinterpret_cast<Dest*>(&source)` that doesn't have
+// undefined behavior (e.g. due to type aliasing).
+// Example: uint64_t d = bit_cast<uint64_t>(2.718);
+template <typename Dest, typename Source>
+inline Dest bit_cast(const Source& source) {
+  static_assert(sizeof(Dest) == sizeof(Source), "size mismatch");
+  Dest dest;
+  std::memcpy(&dest, &source, sizeof(dest));
+  return dest;
+}
+
+inline bool is_big_endian() {
+  const auto u = 1u;
+  struct bytes {
+    char data[sizeof(u)];
+  };
+  return bit_cast<bytes>(u).data[0] == 0;
+}
+
+// A fallback implementation of uintptr_t for systems that lack it.
+struct fallback_uintptr {
+  unsigned char value[sizeof(void*)];
+
+  fallback_uintptr() = default;
+  explicit fallback_uintptr(const void* p) {
+    *this = bit_cast<fallback_uintptr>(p);
+    if (is_big_endian()) {
+      for (size_t i = 0, j = sizeof(void*) - 1; i < j; ++i, --j)
+        std::swap(value[i], value[j]);
+    }
+  }
+};
+#ifdef UINTPTR_MAX
+using uintptr_t = ::uintptr_t;
+inline uintptr_t to_uintptr(const void* p) { return bit_cast<uintptr_t>(p); }
+#else
+using uintptr_t = fallback_uintptr;
+inline fallback_uintptr to_uintptr(const void* p) {
+  return fallback_uintptr(p);
+}
+#endif
+
+// Returns the largest possible value for type T. Same as
+// std::numeric_limits<T>::max() but shorter and not affected by the max macro.
+template <typename T> constexpr T max_value() {
+  return (std::numeric_limits<T>::max)();
+}
+template <typename T> constexpr int num_bits() {
+  return std::numeric_limits<T>::digits;
+}
+// std::numeric_limits<T>::digits may return 0 for 128-bit ints.
+template <> constexpr int num_bits<int128_t>() { return 128; }
+template <> constexpr int num_bits<uint128_t>() { return 128; }
+template <> constexpr int num_bits<fallback_uintptr>() {
+  return static_cast<int>(sizeof(void*) *
+                          std::numeric_limits<unsigned char>::digits);
+}
+
+FMT_INLINE void assume(bool condition) {
+  (void)condition;
+#if FMT_HAS_BUILTIN(__builtin_assume)
+  __builtin_assume(condition);
+#endif
+}
+
+// A workaround for gcc 4.8 to make void_t work in a SFINAE context.
+template <typename... Ts> struct void_t_impl { using type = void; };
+
+template <typename... Ts>
+using void_t = typename detail::void_t_impl<Ts...>::type;
+
+// An approximation of iterator_t for pre-C++20 systems.
+template <typename T>
+using iterator_t = decltype(std::begin(std::declval<T&>()));
+template <typename T> using sentinel_t = decltype(std::end(std::declval<T&>()));
+
+// Detect the iterator category of *any* given type in a SFINAE-friendly way.
+// Unfortunately, older implementations of std::iterator_traits are not safe
+// for use in a SFINAE-context.
+template <typename It, typename Enable = void>
+struct iterator_category : std::false_type {};
+
+template <typename T> struct iterator_category<T*> {
+  using type = std::random_access_iterator_tag;
+};
+
+template <typename It>
+struct iterator_category<It, void_t<typename It::iterator_category>> {
+  using type = typename It::iterator_category;
+};
+
+// Detect if *any* given type models the OutputIterator concept.
+template <typename It> class is_output_iterator {
+  // Check for mutability because all iterator categories derived from
+  // std::input_iterator_tag *may* also meet the requirements of an
+  // OutputIterator, thereby falling into the category of 'mutable iterators'
+  // [iterator.requirements.general] clause 4. The compiler reveals this
+  // property only at the point of *actually dereferencing* the iterator!
+  template <typename U>
+  static decltype(*(std::declval<U>())) test(std::input_iterator_tag);
+  template <typename U> static char& test(std::output_iterator_tag);
+  template <typename U> static const char& test(...);
+
+  using type = decltype(test<It>(typename iterator_category<It>::type{}));
+
+ public:
+  enum { value = !std::is_const<remove_reference_t<type>>::value };
+};
+
+// A workaround for std::string not having mutable data() until C++17.
+template <typename Char> inline Char* get_data(std::basic_string<Char>& s) {
+  return &s[0];
+}
+template <typename Container>
+inline typename Container::value_type* get_data(Container& c) {
+  return c.data();
+}
+
+#if defined(_SECURE_SCL) && _SECURE_SCL
+// Make a checked iterator to avoid MSVC warnings.
+template <typename T> using checked_ptr = stdext::checked_array_iterator<T*>;
+template <typename T> checked_ptr<T> make_checked(T* p, size_t size) {
+  return {p, size};
+}
+#else
+template <typename T> using checked_ptr = T*;
+template <typename T> inline T* make_checked(T* p, size_t) { return p; }
+#endif
+
+template <typename Container, FMT_ENABLE_IF(is_contiguous<Container>::value)>
+#if FMT_CLANG_VERSION
+__attribute__((no_sanitize("undefined")))
+#endif
+inline checked_ptr<typename Container::value_type>
+reserve(std::back_insert_iterator<Container> it, size_t n) {
+  Container& c = get_container(it);
+  size_t size = c.size();
+  c.resize(size + n);
+  return make_checked(get_data(c) + size, n);
+}
+
+template <typename Iterator> inline Iterator& reserve(Iterator& it, size_t) {
+  return it;
+}
+
+template <typename Container, FMT_ENABLE_IF(is_contiguous<Container>::value)>
+inline std::back_insert_iterator<Container> base_iterator(
+    std::back_insert_iterator<Container>& it,
+    checked_ptr<typename Container::value_type>) {
+  return it;
+}
+
+template <typename Iterator>
+inline Iterator base_iterator(Iterator, Iterator it) {
+  return it;
+}
+
+// An output iterator that counts the number of objects written to it and
+// discards them.
+class counting_iterator {
+ private:
+  size_t count_;
+
+ public:
+  using iterator_category = std::output_iterator_tag;
+  using difference_type = std::ptrdiff_t;
+  using pointer = void;
+  using reference = void;
+  using _Unchecked_type = counting_iterator;  // Mark iterator as checked.
+
+  struct value_type {
+    template <typename T> void operator=(const T&) {}
+  };
+
+  counting_iterator() : count_(0) {}
+
+  size_t count() const { return count_; }
+
+  counting_iterator& operator++() {
+    ++count_;
+    return *this;
+  }
+
+  counting_iterator operator++(int) {
+    auto it = *this;
+    ++*this;
+    return it;
+  }
+
+  value_type operator*() const { return {}; }
+};
+
+template <typename OutputIt> class truncating_iterator_base {
+ protected:
+  OutputIt out_;
+  size_t limit_;
+  size_t count_;
+
+  truncating_iterator_base(OutputIt out, size_t limit)
+      : out_(out), limit_(limit), count_(0) {}
+
+ public:
+  using iterator_category = std::output_iterator_tag;
+  using value_type = typename std::iterator_traits<OutputIt>::value_type;
+  using difference_type = void;
+  using pointer = void;
+  using reference = void;
+  using _Unchecked_type =
+      truncating_iterator_base;  // Mark iterator as checked.
+
+  OutputIt base() const { return out_; }
+  size_t count() const { return count_; }
+};
+
+// An output iterator that truncates the output and counts the number of objects
+// written to it.
+template <typename OutputIt,
+          typename Enable = typename std::is_void<
+              typename std::iterator_traits<OutputIt>::value_type>::type>
+class truncating_iterator;
+
+template <typename OutputIt>
+class truncating_iterator<OutputIt, std::false_type>
+    : public truncating_iterator_base<OutputIt> {
+  mutable typename truncating_iterator_base<OutputIt>::value_type blackhole_;
+
+ public:
+  using value_type = typename truncating_iterator_base<OutputIt>::value_type;
+
+  truncating_iterator(OutputIt out, size_t limit)
+      : truncating_iterator_base<OutputIt>(out, limit) {}
+
+  truncating_iterator& operator++() {
+    if (this->count_++ < this->limit_) ++this->out_;
+    return *this;
+  }
+
+  truncating_iterator operator++(int) {
+    auto it = *this;
+    ++*this;
+    return it;
+  }
+
+  value_type& operator*() const {
+    return this->count_ < this->limit_ ? *this->out_ : blackhole_;
+  }
+};
+
+template <typename OutputIt>
+class truncating_iterator<OutputIt, std::true_type>
+    : public truncating_iterator_base<OutputIt> {
+ public:
+  truncating_iterator(OutputIt out, size_t limit)
+      : truncating_iterator_base<OutputIt>(out, limit) {}
+
+  template <typename T> truncating_iterator& operator=(T val) {
+    if (this->count_++ < this->limit_) *this->out_++ = val;
+    return *this;
+  }
+
+  truncating_iterator& operator++() { return *this; }
+  truncating_iterator& operator++(int) { return *this; }
+  truncating_iterator& operator*() { return *this; }
+};
+
+template <typename Char>
+inline size_t count_code_points(basic_string_view<Char> s) {
+  return s.size();
+}
+
+// Counts the number of code points in a UTF-8 string.
+inline size_t count_code_points(basic_string_view<char> s) {
+  const char* data = s.data();
+  size_t num_code_points = 0;
+  for (size_t i = 0, size = s.size(); i != size; ++i) {
+    if ((data[i] & 0xc0) != 0x80) ++num_code_points;
+  }
+  return num_code_points;
+}
+
+inline size_t count_code_points(basic_string_view<char8_type> s) {
+  return count_code_points(basic_string_view<char>(
+      reinterpret_cast<const char*>(s.data()), s.size()));
+}
+
+template <typename Char>
+inline size_t code_point_index(basic_string_view<Char> s, size_t n) {
+  size_t size = s.size();
+  return n < size ? n : size;
+}
+
+// Calculates the index of the nth code point in a UTF-8 string.
+inline size_t code_point_index(basic_string_view<char8_type> s, size_t n) {
+  const char8_type* data = s.data();
+  size_t num_code_points = 0;
+  for (size_t i = 0, size = s.size(); i != size; ++i) {
+    if ((data[i] & 0xc0) != 0x80 && ++num_code_points > n) {
+      return i;
+    }
+  }
+  return s.size();
+}
+
+template <typename InputIt, typename OutChar>
+using needs_conversion = bool_constant<
+    std::is_same<typename std::iterator_traits<InputIt>::value_type,
+                 char>::value &&
+    std::is_same<OutChar, char8_type>::value>;
+
+template <typename OutChar, typename InputIt, typename OutputIt,
+          FMT_ENABLE_IF(!needs_conversion<InputIt, OutChar>::value)>
+OutputIt copy_str(InputIt begin, InputIt end, OutputIt it) {
+  return std::copy(begin, end, it);
+}
+
+template <typename OutChar, typename InputIt, typename OutputIt,
+          FMT_ENABLE_IF(needs_conversion<InputIt, OutChar>::value)>
+OutputIt copy_str(InputIt begin, InputIt end, OutputIt it) {
+  return std::transform(begin, end, it,
+                        [](char c) { return static_cast<char8_type>(c); });
+}
+
+#ifndef FMT_USE_GRISU
+#  define FMT_USE_GRISU 1
+#endif
+
+template <typename T> constexpr bool use_grisu() {
+  return FMT_USE_GRISU && std::numeric_limits<double>::is_iec559 &&
+         sizeof(T) <= sizeof(double);
+}
+
+template <typename T>
+template <typename U>
+void buffer<T>::append(const U* begin, const U* end) {
+  size_t new_size = size_ + to_unsigned(end - begin);
+  reserve(new_size);
+  std::uninitialized_copy(begin, end,
+                          make_checked(ptr_ + size_, capacity_ - size_));
+  size_ = new_size;
+}
+}  // namespace detail
+
+// The number of characters to store in the basic_memory_buffer object itself
+// to avoid dynamic memory allocation.
+enum { inline_buffer_size = 500 };
+
+/**
+  \rst
+  A dynamically growing memory buffer for trivially copyable/constructible types
+  with the first ``SIZE`` elements stored in the object itself.
+
+  You can use one of the following type aliases for common character types:
+
+  +----------------+------------------------------+
+  | Type           | Definition                   |
+  +================+==============================+
+  | memory_buffer  | basic_memory_buffer<char>    |
+  +----------------+------------------------------+
+  | wmemory_buffer | basic_memory_buffer<wchar_t> |
+  +----------------+------------------------------+
+
+  **Example**::
+
+     fmt::memory_buffer out;
+     format_to(out, "The answer is {}.", 42);
+
+  This will append the following output to the ``out`` object:
+
+  .. code-block:: none
+
+     The answer is 42.
+
+  The output can be converted to an ``std::string`` with ``to_string(out)``.
+  \endrst
+ */
+template <typename T, size_t SIZE = inline_buffer_size,
+          typename Allocator = std::allocator<T>>
+class basic_memory_buffer : public detail::buffer<T> {
+ private:
+  T store_[SIZE];
+
+  // Don't inherit from Allocator avoid generating type_info for it.
+  Allocator alloc_;
+
+  // Deallocate memory allocated by the buffer.
+  void deallocate() {
+    T* data = this->data();
+    if (data != store_) alloc_.deallocate(data, this->capacity());
+  }
+
+ protected:
+  void grow(size_t size) FMT_OVERRIDE;
+
+ public:
+  using value_type = T;
+  using const_reference = const T&;
+
+  explicit basic_memory_buffer(const Allocator& alloc = Allocator())
+      : alloc_(alloc) {
+    this->set(store_, SIZE);
+  }
+  ~basic_memory_buffer() FMT_OVERRIDE { deallocate(); }
+
+ private:
+  // Move data from other to this buffer.
+  void move(basic_memory_buffer& other) {
+    alloc_ = std::move(other.alloc_);
+    T* data = other.data();
+    size_t size = other.size(), capacity = other.capacity();
+    if (data == other.store_) {
+      this->set(store_, capacity);
+      std::uninitialized_copy(other.store_, other.store_ + size,
+                              detail::make_checked(store_, capacity));
+    } else {
+      this->set(data, capacity);
+      // Set pointer to the inline array so that delete is not called
+      // when deallocating.
+      other.set(other.store_, 0);
+    }
+    this->resize(size);
+  }
+
+ public:
+  /**
+    \rst
+    Constructs a :class:`fmt::basic_memory_buffer` object moving the content
+    of the other object to it.
+    \endrst
+   */
+  basic_memory_buffer(basic_memory_buffer&& other) FMT_NOEXCEPT { move(other); }
+
+  /**
+    \rst
+    Moves the content of the other ``basic_memory_buffer`` object to this one.
+    \endrst
+   */
+  basic_memory_buffer& operator=(basic_memory_buffer&& other) FMT_NOEXCEPT {
+    FMT_ASSERT(this != &other, "");
+    deallocate();
+    move(other);
+    return *this;
+  }
+
+  // Returns a copy of the allocator associated with this buffer.
+  Allocator get_allocator() const { return alloc_; }
+};
+
+template <typename T, size_t SIZE, typename Allocator>
+void basic_memory_buffer<T, SIZE, Allocator>::grow(size_t size) {
+#ifdef FMT_FUZZ
+  if (size > 5000) throw std::runtime_error("fuzz mode - won't grow that much");
+#endif
+  size_t old_capacity = this->capacity();
+  size_t new_capacity = old_capacity + old_capacity / 2;
+  if (size > new_capacity) new_capacity = size;
+  T* old_data = this->data();
+  T* new_data =
+      std::allocator_traits<Allocator>::allocate(alloc_, new_capacity);
+  // The following code doesn't throw, so the raw pointer above doesn't leak.
+  std::uninitialized_copy(old_data, old_data + this->size(),
+                          detail::make_checked(new_data, new_capacity));
+  this->set(new_data, new_capacity);
+  // deallocate must not throw according to the standard, but even if it does,
+  // the buffer already uses the new storage and will deallocate it in
+  // destructor.
+  if (old_data != store_) alloc_.deallocate(old_data, old_capacity);
+}
+
+using memory_buffer = basic_memory_buffer<char>;
+using wmemory_buffer = basic_memory_buffer<wchar_t>;
+
+template <typename T, size_t SIZE, typename Allocator>
+struct is_contiguous<basic_memory_buffer<T, SIZE, Allocator>> : std::true_type {
+};
+
+/** A formatting error such as invalid format string. */
+FMT_CLASS_API
+class FMT_API format_error : public std::runtime_error {
+ public:
+  explicit format_error(const char* message) : std::runtime_error(message) {}
+  explicit format_error(const std::string& message)
+      : std::runtime_error(message) {}
+  format_error(const format_error&) = default;
+  format_error& operator=(const format_error&) = default;
+  format_error(format_error&&) = default;
+  format_error& operator=(format_error&&) = default;
+  ~format_error() FMT_NOEXCEPT FMT_OVERRIDE;
+};
+
+namespace detail {
+
+template <typename T>
+using is_signed =
+    std::integral_constant<bool, std::numeric_limits<T>::is_signed ||
+                                     std::is_same<T, int128_t>::value>;
+
+// Returns true if value is negative, false otherwise.
+// Same as `value < 0` but doesn't produce warnings if T is an unsigned type.
+template <typename T, FMT_ENABLE_IF(is_signed<T>::value)>
+FMT_CONSTEXPR bool is_negative(T value) {
+  return value < 0;
+}
+template <typename T, FMT_ENABLE_IF(!is_signed<T>::value)>
+FMT_CONSTEXPR bool is_negative(T) {
+  return false;
+}
+
+template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
+FMT_CONSTEXPR bool is_supported_floating_point(T) {
+  return (std::is_same<T, float>::value && FMT_USE_FLOAT) ||
+         (std::is_same<T, double>::value && FMT_USE_DOUBLE) ||
+         (std::is_same<T, long double>::value && FMT_USE_LONG_DOUBLE);
+}
+
+// Smallest of uint32_t, uint64_t, uint128_t that is large enough to
+// represent all values of T.
+template <typename T>
+using uint32_or_64_or_128_t =
+    conditional_t<num_bits<T>() <= 32, uint32_t,
+                  conditional_t<num_bits<T>() <= 64, uint64_t, uint128_t>>;
+
+// Static data is placed in this class template for the header-only config.
+template <typename T = void> struct FMT_EXTERN_TEMPLATE_API basic_data {
+  static const uint64_t powers_of_10_64[];
+  static const uint32_t zero_or_powers_of_10_32[];
+  static const uint64_t zero_or_powers_of_10_64[];
+  static const uint64_t pow10_significands[];
+  static const int16_t pow10_exponents[];
+  // GCC generates slightly better code for pairs than chars.
+  using digit_pair = char[2];
+  static const digit_pair digits[];
+  static const char hex_digits[];
+  static const char foreground_color[];
+  static const char background_color[];
+  static const char reset_color[5];
+  static const wchar_t wreset_color[5];
+  static const char signs[];
+  static const char left_padding_shifts[5];
+  static const char right_padding_shifts[5];
+};
+
+#ifndef FMT_EXPORTED
+FMT_EXTERN template struct basic_data<void>;
+#endif
+
+// This is a struct rather than an alias to avoid shadowing warnings in gcc.
+struct data : basic_data<> {};
+
+#ifdef FMT_BUILTIN_CLZLL
+// Returns the number of decimal digits in n. Leading zeros are not counted
+// except for n == 0 in which case count_digits returns 1.
+inline int count_digits(uint64_t n) {
+  // Based on http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
+  // and the benchmark https://github.com/localvoid/cxx-benchmark-count-digits.
+  int t = (64 - FMT_BUILTIN_CLZLL(n | 1)) * 1233 >> 12;
+  return t - (n < data::zero_or_powers_of_10_64[t]) + 1;
+}
+#else
+// Fallback version of count_digits used when __builtin_clz is not available.
+inline int count_digits(uint64_t n) {
+  int count = 1;
+  for (;;) {
+    // Integer division is slow so do it for a group of four digits instead
+    // of for every digit. The idea comes from the talk by Alexandrescu
+    // "Three Optimization Tips for C++". See speed-test for a comparison.
+    if (n < 10) return count;
+    if (n < 100) return count + 1;
+    if (n < 1000) return count + 2;
+    if (n < 10000) return count + 3;
+    n /= 10000u;
+    count += 4;
+  }
+}
+#endif
+
+#if FMT_USE_INT128
+inline int count_digits(uint128_t n) {
+  int count = 1;
+  for (;;) {
+    // Integer division is slow so do it for a group of four digits instead
+    // of for every digit. The idea comes from the talk by Alexandrescu
+    // "Three Optimization Tips for C++". See speed-test for a comparison.
+    if (n < 10) return count;
+    if (n < 100) return count + 1;
+    if (n < 1000) return count + 2;
+    if (n < 10000) return count + 3;
+    n /= 10000U;
+    count += 4;
+  }
+}
+#endif
+
+// Counts the number of digits in n. BITS = log2(radix).
+template <unsigned BITS, typename UInt> inline int count_digits(UInt n) {
+  int num_digits = 0;
+  do {
+    ++num_digits;
+  } while ((n >>= BITS) != 0);
+  return num_digits;
+}
+
+template <> int count_digits<4>(detail::fallback_uintptr n);
+
+#if FMT_GCC_VERSION || FMT_CLANG_VERSION
+#  define FMT_ALWAYS_INLINE inline __attribute__((always_inline))
+#else
+#  define FMT_ALWAYS_INLINE
+#endif
+
+#ifdef FMT_BUILTIN_CLZ
+// Optional version of count_digits for better performance on 32-bit platforms.
+inline int count_digits(uint32_t n) {
+  int t = (32 - FMT_BUILTIN_CLZ(n | 1)) * 1233 >> 12;
+  return t - (n < data::zero_or_powers_of_10_32[t]) + 1;
+}
+#endif
+
+template <typename Int> constexpr int digits10() FMT_NOEXCEPT {
+  return std::numeric_limits<Int>::digits10;
+}
+template <> constexpr int digits10<int128_t>() FMT_NOEXCEPT { return 38; }
+template <> constexpr int digits10<uint128_t>() FMT_NOEXCEPT { return 38; }
+
+template <typename Char> FMT_API std::string grouping_impl(locale_ref loc);
+template <typename Char> inline std::string grouping(locale_ref loc) {
+  return grouping_impl<char>(loc);
+}
+template <> inline std::string grouping<wchar_t>(locale_ref loc) {
+  return grouping_impl<wchar_t>(loc);
+}
+
+template <typename Char> FMT_API Char thousands_sep_impl(locale_ref loc);
+template <typename Char> inline Char thousands_sep(locale_ref loc) {
+  return Char(thousands_sep_impl<char>(loc));
+}
+template <> inline wchar_t thousands_sep(locale_ref loc) {
+  return thousands_sep_impl<wchar_t>(loc);
+}
+
+template <typename Char> FMT_API Char decimal_point_impl(locale_ref loc);
+template <typename Char> inline Char decimal_point(locale_ref loc) {
+  return Char(decimal_point_impl<char>(loc));
+}
+template <> inline wchar_t decimal_point(locale_ref loc) {
+  return decimal_point_impl<wchar_t>(loc);
+}
+
+// Compares two characters for equality.
+template <typename Char> bool equal2(const Char* lhs, const char* rhs) {
+  return lhs[0] == rhs[0] && lhs[1] == rhs[1];
+}
+inline bool equal2(const char* lhs, const char* rhs) {
+  return memcmp(lhs, rhs, 2) == 0;
+}
+
+// Copies two characters from src to dst.
+template <typename Char> void copy2(Char* dst, const char* src) {
+  *dst++ = static_cast<Char>(*src++);
+  *dst = static_cast<Char>(*src);
+}
+inline void copy2(char* dst, const char* src) { memcpy(dst, src, 2); }
+
+template <typename Iterator> struct format_decimal_result {
+  Iterator begin;
+  Iterator end;
+};
+
+// Formats a decimal unsigned integer value writing into out pointing to a
+// buffer of specified size. The caller must ensure that the buffer is large
+// enough.
+template <typename Char, typename UInt>
+inline format_decimal_result<Char*> format_decimal(Char* out, UInt value,
+                                                   int size) {
+  FMT_ASSERT(size >= count_digits(value), "invalid digit count");
+  out += size;
+  Char* end = out;
+  while (value >= 100) {
+    // Integer division is slow so do it for a group of two digits instead
+    // of for every digit. The idea comes from the talk by Alexandrescu
+    // "Three Optimization Tips for C++". See speed-test for a comparison.
+    out -= 2;
+    copy2(out, data::digits[value % 100]);
+    value /= 100;
+  }
+  if (value < 10) {
+    *--out = static_cast<Char>('0' + value);
+    return {out, end};
+  }
+  out -= 2;
+  copy2(out, data::digits[value]);
+  return {out, end};
+}
+
+template <typename Char, typename UInt, typename Iterator,
+          FMT_ENABLE_IF(!std::is_pointer<remove_cvref_t<Iterator>>::value)>
+inline format_decimal_result<Iterator> format_decimal(Iterator out, UInt value,
+                                                      int num_digits) {
+  // Buffer should be large enough to hold all digits (<= digits10 + 1).
+  enum { max_size = digits10<UInt>() + 1 };
+  Char buffer[2 * max_size];
+  auto end = format_decimal(buffer, value, num_digits).end;
+  return {out, detail::copy_str<Char>(buffer, end, out)};
+}
+
+template <unsigned BASE_BITS, typename Char, typename UInt>
+inline Char* format_uint(Char* buffer, UInt value, int num_digits,
+                         bool upper = false) {
+  buffer += num_digits;
+  Char* end = buffer;
+  do {
+    const char* digits = upper ? "0123456789ABCDEF" : data::hex_digits;
+    unsigned digit = (value & ((1 << BASE_BITS) - 1));
+    *--buffer = static_cast<Char>(BASE_BITS < 4 ? static_cast<char>('0' + digit)
+                                                : digits[digit]);
+  } while ((value >>= BASE_BITS) != 0);
+  return end;
+}
+
+template <unsigned BASE_BITS, typename Char>
+Char* format_uint(Char* buffer, detail::fallback_uintptr n, int num_digits,
+                  bool = false) {
+  auto char_digits = std::numeric_limits<unsigned char>::digits / 4;
+  int start = (num_digits + char_digits - 1) / char_digits - 1;
+  if (int start_digits = num_digits % char_digits) {
+    unsigned value = n.value[start--];
+    buffer = format_uint<BASE_BITS>(buffer, value, start_digits);
+  }
+  for (; start >= 0; --start) {
+    unsigned value = n.value[start];
+    buffer += char_digits;
+    auto p = buffer;
+    for (int i = 0; i < char_digits; ++i) {
+      unsigned digit = (value & ((1 << BASE_BITS) - 1));
+      *--p = static_cast<Char>(data::hex_digits[digit]);
+      value >>= BASE_BITS;
+    }
+  }
+  return buffer;
+}
+
+template <unsigned BASE_BITS, typename Char, typename It, typename UInt>
+inline It format_uint(It out, UInt value, int num_digits, bool upper = false) {
+  // Buffer should be large enough to hold all digits (digits / BASE_BITS + 1).
+  char buffer[num_bits<UInt>() / BASE_BITS + 1];
+  format_uint<BASE_BITS>(buffer, value, num_digits, upper);
+  return detail::copy_str<Char>(buffer, buffer + num_digits, out);
+}
+
+// A converter from UTF-8 to UTF-16.
+class utf8_to_utf16 {
+ private:
+  wmemory_buffer buffer_;
+
+ public:
+  FMT_API explicit utf8_to_utf16(string_view s);
+  operator wstring_view() const { return {&buffer_[0], size()}; }
+  size_t size() const { return buffer_.size() - 1; }
+  const wchar_t* c_str() const { return &buffer_[0]; }
+  std::wstring str() const { return {&buffer_[0], size()}; }
+};
+
+template <typename T = void> struct null {};
+
+// Workaround an array initialization issue in gcc 4.8.
+template <typename Char> struct fill_t {
+ private:
+  enum { max_size = 4 };
+  Char data_[max_size];
+  unsigned char size_;
+
+ public:
+  FMT_CONSTEXPR void operator=(basic_string_view<Char> s) {
+    auto size = s.size();
+    if (size > max_size) {
+      FMT_THROW(format_error("invalid fill"));
+      return;
+    }
+    for (size_t i = 0; i < size; ++i) data_[i] = s[i];
+    size_ = static_cast<unsigned char>(size);
+  }
+
+  size_t size() const { return size_; }
+  const Char* data() const { return data_; }
+
+  FMT_CONSTEXPR Char& operator[](size_t index) { return data_[index]; }
+  FMT_CONSTEXPR const Char& operator[](size_t index) const {
+    return data_[index];
+  }
+
+  static FMT_CONSTEXPR fill_t<Char> make() {
+    auto fill = fill_t<Char>();
+    fill[0] = Char(' ');
+    fill.size_ = 1;
+    return fill;
+  }
+};
+}  // namespace detail
+
+// We cannot use enum classes as bit fields because of a gcc bug
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61414.
+namespace align {
+enum type { none, left, right, center, numeric };
+}
+using align_t = align::type;
+
+namespace sign {
+enum type { none, minus, plus, space };
+}
+using sign_t = sign::type;
+
+// Format specifiers for built-in and string types.
+template <typename Char> struct basic_format_specs {
+  int width;
+  int precision;
+  char type;
+  align_t align : 4;
+  sign_t sign : 3;
+  bool alt : 1;  // Alternate form ('#').
+  detail::fill_t<Char> fill;
+
+  constexpr basic_format_specs()
+      : width(0),
+        precision(-1),
+        type(0),
+        align(align::none),
+        sign(sign::none),
+        alt(false),
+        fill(detail::fill_t<Char>::make()) {}
+};
+
+using format_specs = basic_format_specs<char>;
+
+namespace detail {
+
+// A floating-point presentation format.
+enum class float_format : unsigned char {
+  general,  // General: exponent notation or fixed point based on magnitude.
+  exp,      // Exponent notation with the default precision of 6, e.g. 1.2e-3.
+  fixed,    // Fixed point with the default precision of 6, e.g. 0.0012.
+  hex
+};
+
+struct float_specs {
+  int precision;
+  float_format format : 8;
+  sign_t sign : 8;
+  bool upper : 1;
+  bool locale : 1;
+  bool binary32 : 1;
+  bool use_grisu : 1;
+  bool showpoint : 1;
+};
+
+// Writes the exponent exp in the form "[+-]d{2,3}" to buffer.
+template <typename Char, typename It> It write_exponent(int exp, It it) {
+  FMT_ASSERT(-10000 < exp && exp < 10000, "exponent out of range");
+  if (exp < 0) {
+    *it++ = static_cast<Char>('-');
+    exp = -exp;
+  } else {
+    *it++ = static_cast<Char>('+');
+  }
+  if (exp >= 100) {
+    const char* top = data::digits[exp / 100];
+    if (exp >= 1000) *it++ = static_cast<Char>(top[0]);
+    *it++ = static_cast<Char>(top[1]);
+    exp %= 100;
+  }
+  const char* d = data::digits[exp];
+  *it++ = static_cast<Char>(d[0]);
+  *it++ = static_cast<Char>(d[1]);
+  return it;
+}
+
+template <typename Char> class float_writer {
+ private:
+  // The number is given as v = digits_ * pow(10, exp_).
+  const char* digits_;
+  int num_digits_;
+  int exp_;
+  size_t size_;
+  float_specs specs_;
+  Char decimal_point_;
+
+  template <typename It> It prettify(It it) const {
+    // pow(10, full_exp - 1) <= v <= pow(10, full_exp).
+    int full_exp = num_digits_ + exp_;
+    if (specs_.format == float_format::exp) {
+      // Insert a decimal point after the first digit and add an exponent.
+      *it++ = static_cast<Char>(*digits_);
+      int num_zeros = specs_.precision - num_digits_;
+      if (num_digits_ > 1 || specs_.showpoint) *it++ = decimal_point_;
+      it = copy_str<Char>(digits_ + 1, digits_ + num_digits_, it);
+      if (num_zeros > 0 && specs_.showpoint)
+        it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
+      *it++ = static_cast<Char>(specs_.upper ? 'E' : 'e');
+      return write_exponent<Char>(full_exp - 1, it);
+    }
+    if (num_digits_ <= full_exp) {
+      // 1234e7 -> 12340000000[.0+]
+      it = copy_str<Char>(digits_, digits_ + num_digits_, it);
+      it = std::fill_n(it, full_exp - num_digits_, static_cast<Char>('0'));
+      if (specs_.showpoint || specs_.precision < 0) {
+        *it++ = decimal_point_;
+        int num_zeros = specs_.precision - full_exp;
+        if (num_zeros <= 0) {
+          if (specs_.format != float_format::fixed)
+            *it++ = static_cast<Char>('0');
+          return it;
+        }
+#ifdef FMT_FUZZ
+        if (num_zeros > 5000)
+          throw std::runtime_error("fuzz mode - avoiding excessive cpu use");
+#endif
+        it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
+      }
+    } else if (full_exp > 0) {
+      // 1234e-2 -> 12.34[0+]
+      it = copy_str<Char>(digits_, digits_ + full_exp, it);
+      if (!specs_.showpoint) {
+        // Remove trailing zeros.
+        int num_digits = num_digits_;
+        while (num_digits > full_exp && digits_[num_digits - 1] == '0')
+          --num_digits;
+        if (num_digits != full_exp) *it++ = decimal_point_;
+        return copy_str<Char>(digits_ + full_exp, digits_ + num_digits, it);
+      }
+      *it++ = decimal_point_;
+      it = copy_str<Char>(digits_ + full_exp, digits_ + num_digits_, it);
+      if (specs_.precision > num_digits_) {
+        // Add trailing zeros.
+        int num_zeros = specs_.precision - num_digits_;
+        it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
+      }
+    } else {
+      // 1234e-6 -> 0.001234
+      *it++ = static_cast<Char>('0');
+      int num_zeros = -full_exp;
+      int num_digits = num_digits_;
+      if (num_digits == 0 && specs_.precision >= 0 &&
+          specs_.precision < num_zeros) {
+        num_zeros = specs_.precision;
+      }
+      // Remove trailing zeros.
+      if (!specs_.showpoint)
+        while (num_digits > 0 && digits_[num_digits - 1] == '0') --num_digits;
+      if (num_zeros != 0 || num_digits != 0 || specs_.showpoint) {
+        *it++ = decimal_point_;
+        it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
+        it = copy_str<Char>(digits_, digits_ + num_digits, it);
+      }
+    }
+    return it;
+  }
+
+ public:
+  float_writer(const char* digits, int num_digits, int exp, float_specs specs,
+               Char decimal_point)
+      : digits_(digits),
+        num_digits_(num_digits),
+        exp_(exp),
+        specs_(specs),
+        decimal_point_(decimal_point) {
+    int full_exp = num_digits + exp - 1;
+    int precision = specs.precision > 0 ? specs.precision : 16;
+    if (specs_.format == float_format::general &&
+        !(full_exp >= -4 && full_exp < precision)) {
+      specs_.format = float_format::exp;
+    }
+    size_ = prettify(counting_iterator()).count();
+    size_ += specs.sign ? 1 : 0;
+  }
+
+  size_t size() const { return size_; }
+
+  template <typename It> It operator()(It it) const {
+    if (specs_.sign) *it++ = static_cast<Char>(data::signs[specs_.sign]);
+    return prettify(it);
+  }
+};
+
+template <typename T>
+int format_float(T value, int precision, float_specs specs, buffer<char>& buf);
+
+// Formats a floating-point number with snprintf.
+template <typename T>
+int snprintf_float(T value, int precision, float_specs specs,
+                   buffer<char>& buf);
+
+template <typename T> T promote_float(T value) { return value; }
+inline double promote_float(float value) { return static_cast<double>(value); }
+
+template <typename Handler>
+FMT_CONSTEXPR void handle_int_type_spec(char spec, Handler&& handler) {
+  switch (spec) {
+  case 0:
+  case 'd':
+    handler.on_dec();
+    break;
+  case 'x':
+  case 'X':
+    handler.on_hex();
+    break;
+  case 'b':
+  case 'B':
+    handler.on_bin();
+    break;
+  case 'o':
+    handler.on_oct();
+    break;
+#ifdef FMT_DEPRECATED_N_SPECIFIER
+  case 'n':
+#endif
+  case 'L':
+    handler.on_num();
+    break;
+  case 'c':
+    handler.on_chr();
+    break;
+  default:
+    handler.on_error();
+  }
+}
+
+template <typename ErrorHandler = error_handler, typename Char>
+FMT_CONSTEXPR float_specs parse_float_type_spec(
+    const basic_format_specs<Char>& specs, ErrorHandler&& eh = {}) {
+  auto result = float_specs();
+  result.showpoint = specs.alt;
+  switch (specs.type) {
+  case 0:
+    result.format = float_format::general;
+    result.showpoint |= specs.precision > 0;
+    break;
+  case 'G':
+    result.upper = true;
+    FMT_FALLTHROUGH;
+  case 'g':
+    result.format = float_format::general;
+    break;
+  case 'E':
+    result.upper = true;
+    FMT_FALLTHROUGH;
+  case 'e':
+    result.format = float_format::exp;
+    result.showpoint |= specs.precision != 0;
+    break;
+  case 'F':
+    result.upper = true;
+    FMT_FALLTHROUGH;
+  case 'f':
+    result.format = float_format::fixed;
+    result.showpoint |= specs.precision != 0;
+    break;
+  case 'A':
+    result.upper = true;
+    FMT_FALLTHROUGH;
+  case 'a':
+    result.format = float_format::hex;
+    break;
+#ifdef FMT_DEPRECATED_N_SPECIFIER
+  case 'n':
+#endif
+  case 'L':
+    result.locale = true;
+    break;
+  default:
+    eh.on_error("invalid type specifier");
+    break;
+  }
+  return result;
+}
+
+template <typename Char, typename Handler>
+FMT_CONSTEXPR void handle_char_specs(const basic_format_specs<Char>* specs,
+                                     Handler&& handler) {
+  if (!specs) return handler.on_char();
+  if (specs->type && specs->type != 'c') return handler.on_int();
+  if (specs->align == align::numeric || specs->sign != sign::none || specs->alt)
+    handler.on_error("invalid format specifier for char");
+  handler.on_char();
+}
+
+template <typename Char, typename Handler>
+FMT_CONSTEXPR void handle_cstring_type_spec(Char spec, Handler&& handler) {
+  if (spec == 0 || spec == 's')
+    handler.on_string();
+  else if (spec == 'p')
+    handler.on_pointer();
+  else
+    handler.on_error("invalid type specifier");
+}
+
+template <typename Char, typename ErrorHandler>
+FMT_CONSTEXPR void check_string_type_spec(Char spec, ErrorHandler&& eh) {
+  if (spec != 0 && spec != 's') eh.on_error("invalid type specifier");
+}
+
+template <typename Char, typename ErrorHandler>
+FMT_CONSTEXPR void check_pointer_type_spec(Char spec, ErrorHandler&& eh) {
+  if (spec != 0 && spec != 'p') eh.on_error("invalid type specifier");
+}
+
+template <typename ErrorHandler> class int_type_checker : private ErrorHandler {
+ public:
+  FMT_CONSTEXPR explicit int_type_checker(ErrorHandler eh) : ErrorHandler(eh) {}
+
+  FMT_CONSTEXPR void on_dec() {}
+  FMT_CONSTEXPR void on_hex() {}
+  FMT_CONSTEXPR void on_bin() {}
+  FMT_CONSTEXPR void on_oct() {}
+  FMT_CONSTEXPR void on_num() {}
+  FMT_CONSTEXPR void on_chr() {}
+
+  FMT_CONSTEXPR void on_error() {
+    ErrorHandler::on_error("invalid type specifier");
+  }
+};
+
+template <typename ErrorHandler>
+class char_specs_checker : public ErrorHandler {
+ private:
+  char type_;
+
+ public:
+  FMT_CONSTEXPR char_specs_checker(char type, ErrorHandler eh)
+      : ErrorHandler(eh), type_(type) {}
+
+  FMT_CONSTEXPR void on_int() {
+    handle_int_type_spec(type_, int_type_checker<ErrorHandler>(*this));
+  }
+  FMT_CONSTEXPR void on_char() {}
+};
+
+template <typename ErrorHandler>
+class cstring_type_checker : public ErrorHandler {
+ public:
+  FMT_CONSTEXPR explicit cstring_type_checker(ErrorHandler eh)
+      : ErrorHandler(eh) {}
+
+  FMT_CONSTEXPR void on_string() {}
+  FMT_CONSTEXPR void on_pointer() {}
+};
+
+template <typename OutputIt, typename Char>
+FMT_NOINLINE OutputIt fill(OutputIt it, size_t n, const fill_t<Char>& fill) {
+  auto fill_size = fill.size();
+  if (fill_size == 1) return std::fill_n(it, n, fill[0]);
+  for (size_t i = 0; i < n; ++i) it = std::copy_n(fill.data(), fill_size, it);
+  return it;
+}
+
+// Writes the output of f, padded according to format specifications in specs.
+// size: output size in code units.
+// width: output display width in (terminal) column positions.
+template <align::type align = align::left, typename OutputIt, typename Char,
+          typename F>
+inline OutputIt write_padded(OutputIt out,
+                             const basic_format_specs<Char>& specs, size_t size,
+                             size_t width, const F& f) {
+  static_assert(align == align::left || align == align::right, "");
+  unsigned spec_width = to_unsigned(specs.width);
+  size_t padding = spec_width > width ? spec_width - width : 0;
+  auto* shifts = align == align::left ? data::left_padding_shifts
+                                      : data::right_padding_shifts;
+  size_t left_padding = padding >> shifts[specs.align];
+  auto it = reserve(out, size + padding * specs.fill.size());
+  it = fill(it, left_padding, specs.fill);
+  it = f(it);
+  it = fill(it, padding - left_padding, specs.fill);
+  return base_iterator(out, it);
+}
+
+template <align::type align = align::left, typename OutputIt, typename Char,
+          typename F>
+inline OutputIt write_padded(OutputIt out,
+                             const basic_format_specs<Char>& specs, size_t size,
+                             const F& f) {
+  return write_padded<align>(out, specs, size, size, f);
+}
+
+template <typename Char, typename OutputIt>
+OutputIt write_bytes(OutputIt out, string_view bytes,
+                     const basic_format_specs<Char>& specs) {
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  return write_padded(out, specs, bytes.size(), [bytes](iterator it) {
+    const char* data = bytes.data();
+    return copy_str<Char>(data, data + bytes.size(), it);
+  });
+}
+
+// Data for write_int that doesn't depend on output iterator type. It is used to
+// avoid template code bloat.
+template <typename Char> struct write_int_data {
+  size_t size;
+  size_t padding;
+
+  write_int_data(int num_digits, string_view prefix,
+                 const basic_format_specs<Char>& specs)
+      : size(prefix.size() + to_unsigned(num_digits)), padding(0) {
+    if (specs.align == align::numeric) {
+      auto width = to_unsigned(specs.width);
+      if (width > size) {
+        padding = width - size;
+        size = width;
+      }
+    } else if (specs.precision > num_digits) {
+      size = prefix.size() + to_unsigned(specs.precision);
+      padding = to_unsigned(specs.precision - num_digits);
+    }
+  }
+};
+
+// Writes an integer in the format
+//   <left-padding><prefix><numeric-padding><digits><right-padding>
+// where <digits> are written by f(it).
+template <typename OutputIt, typename Char, typename F>
+OutputIt write_int(OutputIt out, int num_digits, string_view prefix,
+                   const basic_format_specs<Char>& specs, F f) {
+  auto data = write_int_data<Char>(num_digits, prefix, specs);
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  return write_padded<align::right>(out, specs, data.size, [=](iterator it) {
+    if (prefix.size() != 0)
+      it = copy_str<Char>(prefix.begin(), prefix.end(), it);
+    it = std::fill_n(it, data.padding, static_cast<Char>('0'));
+    return f(it);
+  });
+}
+
+template <typename StrChar, typename Char, typename OutputIt>
+OutputIt write(OutputIt out, basic_string_view<StrChar> s,
+               const basic_format_specs<Char>& specs) {
+  auto data = s.data();
+  auto size = s.size();
+  if (specs.precision >= 0 && to_unsigned(specs.precision) < size)
+    size = code_point_index(s, to_unsigned(specs.precision));
+  auto width = specs.width != 0
+                   ? count_code_points(basic_string_view<StrChar>(data, size))
+                   : 0;
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  return write_padded(out, specs, size, width, [=](iterator it) {
+    return copy_str<Char>(data, data + size, it);
+  });
+}
+
+// The handle_int_type_spec handler that writes an integer.
+template <typename OutputIt, typename Char, typename UInt> struct int_writer {
+  OutputIt out;
+  locale_ref locale;
+  const basic_format_specs<Char>& specs;
+  UInt abs_value;
+  char prefix[4];
+  unsigned prefix_size;
+
+  using iterator =
+      remove_reference_t<decltype(reserve(std::declval<OutputIt&>(), 0))>;
+
+  string_view get_prefix() const { return string_view(prefix, prefix_size); }
+
+  template <typename Int>
+  int_writer(OutputIt output, locale_ref loc, Int value,
+             const basic_format_specs<Char>& s)
+      : out(output),
+        locale(loc),
+        specs(s),
+        abs_value(static_cast<UInt>(value)),
+        prefix_size(0) {
+    static_assert(std::is_same<uint32_or_64_or_128_t<Int>, UInt>::value, "");
+    if (is_negative(value)) {
+      prefix[0] = '-';
+      ++prefix_size;
+      abs_value = 0 - abs_value;
+    } else if (specs.sign != sign::none && specs.sign != sign::minus) {
+      prefix[0] = specs.sign == sign::plus ? '+' : ' ';
+      ++prefix_size;
+    }
+  }
+
+  void on_dec() {
+    auto num_digits = count_digits(abs_value);
+    out = write_int(
+        out, num_digits, get_prefix(), specs, [this, num_digits](iterator it) {
+          return format_decimal<Char>(it, abs_value, num_digits).end;
+        });
+  }
+
+  void on_hex() {
+    if (specs.alt) {
+      prefix[prefix_size++] = '0';
+      prefix[prefix_size++] = specs.type;
+    }
+    int num_digits = count_digits<4>(abs_value);
+    out = write_int(out, num_digits, get_prefix(), specs,
+                    [this, num_digits](iterator it) {
+                      return format_uint<4, Char>(it, abs_value, num_digits,
+                                                  specs.type != 'x');
+                    });
+  }
+
+  void on_bin() {
+    if (specs.alt) {
+      prefix[prefix_size++] = '0';
+      prefix[prefix_size++] = static_cast<char>(specs.type);
+    }
+    int num_digits = count_digits<1>(abs_value);
+    out = write_int(out, num_digits, get_prefix(), specs,
+                    [this, num_digits](iterator it) {
+                      return format_uint<1, Char>(it, abs_value, num_digits);
+                    });
+  }
+
+  void on_oct() {
+    int num_digits = count_digits<3>(abs_value);
+    if (specs.alt && specs.precision <= num_digits && abs_value != 0) {
+      // Octal prefix '0' is counted as a digit, so only add it if precision
+      // is not greater than the number of digits.
+      prefix[prefix_size++] = '0';
+    }
+    out = write_int(out, num_digits, get_prefix(), specs,
+                    [this, num_digits](iterator it) {
+                      return format_uint<3, Char>(it, abs_value, num_digits);
+                    });
+  }
+
+  enum { sep_size = 1 };
+
+  void on_num() {
+    std::string groups = grouping<Char>(locale);
+    if (groups.empty()) return on_dec();
+    auto sep = thousands_sep<Char>(locale);
+    if (!sep) return on_dec();
+    int num_digits = count_digits(abs_value);
+    int size = num_digits, n = num_digits;
+    std::string::const_iterator group = groups.cbegin();
+    while (group != groups.cend() && n > *group && *group > 0 &&
+           *group != max_value<char>()) {
+      size += sep_size;
+      n -= *group;
+      ++group;
+    }
+    if (group == groups.cend()) size += sep_size * ((n - 1) / groups.back());
+    char digits[40];
+    format_decimal(digits, abs_value, num_digits);
+    basic_memory_buffer<Char> buffer;
+    size += prefix_size;
+    buffer.resize(size);
+    basic_string_view<Char> s(&sep, sep_size);
+    // Index of a decimal digit with the least significant digit having index 0.
+    int digit_index = 0;
+    group = groups.cbegin();
+    auto p = buffer.data() + size;
+    for (int i = num_digits - 1; i >= 0; --i) {
+      *--p = static_cast<Char>(digits[i]);
+      if (*group <= 0 || ++digit_index % *group != 0 ||
+          *group == max_value<char>())
+        continue;
+      if (group + 1 != groups.cend()) {
+        digit_index = 0;
+        ++group;
+      }
+      p -= s.size();
+      std::uninitialized_copy(s.data(), s.data() + s.size(),
+                              make_checked(p, s.size()));
+    }
+    if (prefix_size != 0) p[-1] = static_cast<Char>('-');
+    using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+    auto data = buffer.data();
+    out = write_padded<align::right>(out, specs, size, size, [=](iterator it) {
+      return copy_str<Char>(data, data + size, it);
+    });
+  }
+
+  void on_chr() { *out++ = static_cast<Char>(abs_value); }
+
+  FMT_NORETURN void on_error() {
+    FMT_THROW(format_error("invalid type specifier"));
+  }
+};
+
+template <typename Char, typename OutputIt>
+OutputIt write_nonfinite(OutputIt out, bool isinf,
+                         const basic_format_specs<Char>& specs,
+                         const float_specs& fspecs) {
+  auto str =
+      isinf ? (fspecs.upper ? "INF" : "inf") : (fspecs.upper ? "NAN" : "nan");
+  constexpr size_t str_size = 3;
+  auto sign = fspecs.sign;
+  auto size = str_size + (sign ? 1 : 0);
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  return write_padded(out, specs, size, [=](iterator it) {
+    if (sign) *it++ = static_cast<Char>(data::signs[sign]);
+    return copy_str<Char>(str, str + str_size, it);
+  });
+}
+
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(std::is_floating_point<T>::value)>
+OutputIt write(OutputIt out, T value, basic_format_specs<Char> specs,
+               locale_ref loc = {}) {
+  if (const_check(!is_supported_floating_point(value))) return out;
+  float_specs fspecs = parse_float_type_spec(specs);
+  fspecs.sign = specs.sign;
+  if (std::signbit(value)) {  // value < 0 is false for NaN so use signbit.
+    fspecs.sign = sign::minus;
+    value = -value;
+  } else if (fspecs.sign == sign::minus) {
+    fspecs.sign = sign::none;
+  }
+
+  if (!std::isfinite(value))
+    return write_nonfinite(out, std::isinf(value), specs, fspecs);
+
+  if (specs.align == align::numeric && fspecs.sign) {
+    auto it = reserve(out, 1);
+    *it++ = static_cast<Char>(data::signs[fspecs.sign]);
+    out = base_iterator(out, it);
+    fspecs.sign = sign::none;
+    if (specs.width != 0) --specs.width;
+  }
+
+  memory_buffer buffer;
+  if (fspecs.format == float_format::hex) {
+    if (fspecs.sign) buffer.push_back(data::signs[fspecs.sign]);
+    snprintf_float(promote_float(value), specs.precision, fspecs, buffer);
+    return write_bytes(out, {buffer.data(), buffer.size()}, specs);
+  }
+  int precision = specs.precision >= 0 || !specs.type ? specs.precision : 6;
+  if (fspecs.format == float_format::exp) {
+    if (precision == max_value<int>())
+      FMT_THROW(format_error("number is too big"));
+    else
+      ++precision;
+  }
+  if (const_check(std::is_same<T, float>())) fspecs.binary32 = true;
+  fspecs.use_grisu = use_grisu<T>();
+  int exp = format_float(promote_float(value), precision, fspecs, buffer);
+  fspecs.precision = precision;
+  Char point =
+      fspecs.locale ? decimal_point<Char>(loc) : static_cast<Char>('.');
+  float_writer<Char> w(buffer.data(), static_cast<int>(buffer.size()), exp,
+                       fspecs, point);
+  return write_padded<align::right>(out, specs, w.size(), w);
+}
+
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(std::is_floating_point<T>::value)>
+OutputIt write(OutputIt out, T value) {
+  if (const_check(!is_supported_floating_point(value))) return out;
+  auto fspecs = float_specs();
+  if (std::signbit(value)) {  // value < 0 is false for NaN so use signbit.
+    fspecs.sign = sign::minus;
+    value = -value;
+  }
+
+  auto specs = basic_format_specs<Char>();
+  if (!std::isfinite(value))
+    return write_nonfinite(out, std::isinf(value), specs, fspecs);
+
+  memory_buffer buffer;
+  int precision = -1;
+  if (const_check(std::is_same<T, float>())) fspecs.binary32 = true;
+  fspecs.use_grisu = use_grisu<T>();
+  int exp = format_float(promote_float(value), precision, fspecs, buffer);
+  fspecs.precision = precision;
+  float_writer<Char> w(buffer.data(), static_cast<int>(buffer.size()), exp,
+                       fspecs, static_cast<Char>('.'));
+  return base_iterator(out, w(reserve(out, w.size())));
+}
+
+template <typename Char, typename OutputIt>
+OutputIt write_char(OutputIt out, Char value,
+                    const basic_format_specs<Char>& specs) {
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  return write_padded(out, specs, 1, [=](iterator it) {
+    *it++ = value;
+    return it;
+  });
+}
+
+template <typename Char, typename OutputIt, typename UIntPtr>
+OutputIt write_ptr(OutputIt out, UIntPtr value,
+                   const basic_format_specs<Char>* specs) {
+  int num_digits = count_digits<4>(value);
+  auto size = to_unsigned(num_digits) + size_t(2);
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  auto write = [=](iterator it) {
+    *it++ = static_cast<Char>('0');
+    *it++ = static_cast<Char>('x');
+    return format_uint<4, Char>(it, value, num_digits);
+  };
+  return specs ? write_padded<align::right>(out, *specs, size, write)
+               : base_iterator(out, write(reserve(out, size)));
+}
+
+template <typename T> struct is_integral : std::is_integral<T> {};
+template <> struct is_integral<int128_t> : std::true_type {};
+template <> struct is_integral<uint128_t> : std::true_type {};
+
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, monostate) {
+  FMT_ASSERT(false, "");
+  return out;
+}
+
+template <typename Char, typename OutputIt,
+          FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
+OutputIt write(OutputIt out, string_view value) {
+  auto it = reserve(out, value.size());
+  it = copy_str<Char>(value.begin(), value.end(), it);
+  return base_iterator(out, it);
+}
+
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, basic_string_view<Char> value) {
+  auto it = reserve(out, value.size());
+  it = std::copy(value.begin(), value.end(), it);
+  return base_iterator(out, it);
+}
+
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(is_integral<T>::value &&
+                        !std::is_same<T, bool>::value &&
+                        !std::is_same<T, Char>::value)>
+OutputIt write(OutputIt out, T value) {
+  auto abs_value = static_cast<uint32_or_64_or_128_t<T>>(value);
+  bool negative = is_negative(value);
+  // Don't do -abs_value since it trips unsigned-integer-overflow sanitizer.
+  if (negative) abs_value = ~abs_value + 1;
+  int num_digits = count_digits(abs_value);
+  auto it = reserve(out, (negative ? 1 : 0) + static_cast<size_t>(num_digits));
+  if (negative) *it++ = static_cast<Char>('-');
+  it = format_decimal<Char>(it, abs_value, num_digits).end;
+  return base_iterator(out, it);
+}
+
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, bool value) {
+  return write<Char>(out, string_view(value ? "true" : "false"));
+}
+
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, Char value) {
+  auto it = reserve(out, 1);
+  *it++ = value;
+  return base_iterator(out, it);
+}
+
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, const Char* value) {
+  if (!value) {
+    FMT_THROW(format_error("string pointer is null"));
+  } else {
+    auto length = std::char_traits<Char>::length(value);
+    out = write(out, basic_string_view<Char>(value, length));
+  }
+  return out;
+}
+
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, const void* value) {
+  return write_ptr<Char>(out, to_uintptr(value), nullptr);
+}
+
+template <typename Char, typename OutputIt, typename T>
+auto write(OutputIt out, const T& value) -> typename std::enable_if<
+    mapped_type_constant<T, basic_format_context<OutputIt, Char>>::value ==
+        type::custom_type,
+    OutputIt>::type {
+  basic_format_context<OutputIt, Char> ctx(out, {}, {});
+  return formatter<T>().format(value, ctx);
+}
+
+// An argument visitor that formats the argument and writes it via the output
+// iterator. It's a class and not a generic lambda for compatibility with C++11.
+template <typename OutputIt, typename Char> struct default_arg_formatter {
+  using context = basic_format_context<OutputIt, Char>;
+
+  OutputIt out;
+  basic_format_args<context> args;
+  locale_ref loc;
+
+  template <typename T> OutputIt operator()(T value) {
+    return write<Char>(out, value);
+  }
+
+  OutputIt operator()(typename basic_format_arg<context>::handle handle) {
+    basic_format_parse_context<Char> parse_ctx({});
+    basic_format_context<OutputIt, Char> format_ctx(out, args, loc);
+    handle.format(parse_ctx, format_ctx);
+    return format_ctx.out();
+  }
+};
+
+template <typename OutputIt, typename Char,
+          typename ErrorHandler = error_handler>
+class arg_formatter_base {
+ public:
+  using iterator = OutputIt;
+  using char_type = Char;
+  using format_specs = basic_format_specs<Char>;
+
+ private:
+  iterator out_;
+  locale_ref locale_;
+  format_specs* specs_;
+
+  // Attempts to reserve space for n extra characters in the output range.
+  // Returns a pointer to the reserved range or a reference to out_.
+  auto reserve(size_t n) -> decltype(detail::reserve(out_, n)) {
+    return detail::reserve(out_, n);
+  }
+
+  using reserve_iterator = remove_reference_t<decltype(
+      detail::reserve(std::declval<iterator&>(), 0))>;
+
+  template <typename T> void write_int(T value, const format_specs& spec) {
+    using uint_type = uint32_or_64_or_128_t<T>;
+    int_writer<iterator, Char, uint_type> w(out_, locale_, value, spec);
+    handle_int_type_spec(spec.type, w);
+    out_ = w.out;
+  }
+
+  void write(char value) {
+    auto&& it = reserve(1);
+    *it++ = value;
+  }
+
+  template <typename Ch, FMT_ENABLE_IF(std::is_same<Ch, Char>::value)>
+  void write(Ch value) {
+    out_ = detail::write<Char>(out_, value);
+  }
+
+  void write(string_view value) {
+    auto&& it = reserve(value.size());
+    it = copy_str<Char>(value.begin(), value.end(), it);
+  }
+  void write(wstring_view value) {
+    static_assert(std::is_same<Char, wchar_t>::value, "");
+    auto&& it = reserve(value.size());
+    it = std::copy(value.begin(), value.end(), it);
+  }
+
+  template <typename Ch>
+  void write(const Ch* s, size_t size, const format_specs& specs) {
+    auto width = specs.width != 0
+                     ? count_code_points(basic_string_view<Ch>(s, size))
+                     : 0;
+    out_ = write_padded(out_, specs, size, width, [=](reserve_iterator it) {
+      return copy_str<Char>(s, s + size, it);
+    });
+  }
+
+  template <typename Ch>
+  void write(basic_string_view<Ch> s, const format_specs& specs = {}) {
+    out_ = detail::write(out_, s, specs);
+  }
+
+  void write_pointer(const void* p) {
+    out_ = write_ptr<char_type>(out_, to_uintptr(p), specs_);
+  }
+
+  struct char_spec_handler : ErrorHandler {
+    arg_formatter_base& formatter;
+    Char value;
+
+    char_spec_handler(arg_formatter_base& f, Char val)
+        : formatter(f), value(val) {}
+
+    void on_int() {
+      // char is only formatted as int if there are specs.
+      formatter.write_int(static_cast<int>(value), *formatter.specs_);
+    }
+    void on_char() {
+      if (formatter.specs_)
+        formatter.out_ = write_char(formatter.out_, value, *formatter.specs_);
+      else
+        formatter.write(value);
+    }
+  };
+
+  struct cstring_spec_handler : error_handler {
+    arg_formatter_base& formatter;
+    const Char* value;
+
+    cstring_spec_handler(arg_formatter_base& f, const Char* val)
+        : formatter(f), value(val) {}
+
+    void on_string() { formatter.write(value); }
+    void on_pointer() { formatter.write_pointer(value); }
+  };
+
+ protected:
+  iterator out() { return out_; }
+  format_specs* specs() { return specs_; }
+
+  void write(bool value) {
+    if (specs_)
+      write(string_view(value ? "true" : "false"), *specs_);
+    else
+      out_ = detail::write<Char>(out_, value);
+  }
+
+  void write(const Char* value) {
+    if (!value) {
+      FMT_THROW(format_error("string pointer is null"));
+    } else {
+      auto length = std::char_traits<char_type>::length(value);
+      basic_string_view<char_type> sv(value, length);
+      specs_ ? write(sv, *specs_) : write(sv);
+    }
+  }
+
+ public:
+  arg_formatter_base(OutputIt out, format_specs* s, locale_ref loc)
+      : out_(out), locale_(loc), specs_(s) {}
+
+  iterator operator()(monostate) {
+    FMT_ASSERT(false, "invalid argument type");
+    return out_;
+  }
+
+  template <typename T, FMT_ENABLE_IF(is_integral<T>::value)>
+  FMT_INLINE iterator operator()(T value) {
+    if (specs_)
+      write_int(value, *specs_);
+    else
+      out_ = detail::write<Char>(out_, value);
+    return out_;
+  }
+
+  iterator operator()(Char value) {
+    handle_char_specs(specs_,
+                      char_spec_handler(*this, static_cast<Char>(value)));
+    return out_;
+  }
+
+  iterator operator()(bool value) {
+    if (specs_ && specs_->type) return (*this)(value ? 1 : 0);
+    write(value != 0);
+    return out_;
+  }
+
+  template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
+  iterator operator()(T value) {
+    auto specs = specs_ ? *specs_ : format_specs();
+    if (const_check(is_supported_floating_point(value)))
+      out_ = detail::write(out_, value, specs, locale_);
+    else
+      FMT_ASSERT(false, "unsupported float argument type");
+    return out_;
+  }
+
+  iterator operator()(const Char* value) {
+    if (!specs_) return write(value), out_;
+    handle_cstring_type_spec(specs_->type, cstring_spec_handler(*this, value));
+    return out_;
+  }
+
+  iterator operator()(basic_string_view<Char> value) {
+    if (specs_) {
+      check_string_type_spec(specs_->type, error_handler());
+      write(value, *specs_);
+    } else {
+      write(value);
+    }
+    return out_;
+  }
+
+  iterator operator()(const void* value) {
+    if (specs_) check_pointer_type_spec(specs_->type, error_handler());
+    write_pointer(value);
+    return out_;
+  }
+};
+
+template <typename Char> FMT_CONSTEXPR bool is_name_start(Char c) {
+  return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || '_' == c;
+}
+
+// Parses the range [begin, end) as an unsigned integer. This function assumes
+// that the range is non-empty and the first character is a digit.
+template <typename Char, typename ErrorHandler>
+FMT_CONSTEXPR int parse_nonnegative_int(const Char*& begin, const Char* end,
+                                        ErrorHandler&& eh) {
+  FMT_ASSERT(begin != end && '0' <= *begin && *begin <= '9', "");
+  unsigned value = 0;
+  // Convert to unsigned to prevent a warning.
+  constexpr unsigned max_int = max_value<int>();
+  unsigned big = max_int / 10;
+  do {
+    // Check for overflow.
+    if (value > big) {
+      value = max_int + 1;
+      break;
+    }
+    value = value * 10 + unsigned(*begin - '0');
+    ++begin;
+  } while (begin != end && '0' <= *begin && *begin <= '9');
+  if (value > max_int) eh.on_error("number is too big");
+  return static_cast<int>(value);
+}
+
+template <typename Context> class custom_formatter {
+ private:
+  using char_type = typename Context::char_type;
+
+  basic_format_parse_context<char_type>& parse_ctx_;
+  Context& ctx_;
+
+ public:
+  explicit custom_formatter(basic_format_parse_context<char_type>& parse_ctx,
+                            Context& ctx)
+      : parse_ctx_(parse_ctx), ctx_(ctx) {}
+
+  bool operator()(typename basic_format_arg<Context>::handle h) const {
+    h.format(parse_ctx_, ctx_);
+    return true;
+  }
+
+  template <typename T> bool operator()(T) const { return false; }
+};
+
+template <typename T>
+using is_integer =
+    bool_constant<is_integral<T>::value && !std::is_same<T, bool>::value &&
+                  !std::is_same<T, char>::value &&
+                  !std::is_same<T, wchar_t>::value>;
+
+template <typename ErrorHandler> class width_checker {
+ public:
+  explicit FMT_CONSTEXPR width_checker(ErrorHandler& eh) : handler_(eh) {}
+
+  template <typename T, FMT_ENABLE_IF(is_integer<T>::value)>
+  FMT_CONSTEXPR unsigned long long operator()(T value) {
+    if (is_negative(value)) handler_.on_error("negative width");
+    return static_cast<unsigned long long>(value);
+  }
+
+  template <typename T, FMT_ENABLE_IF(!is_integer<T>::value)>
+  FMT_CONSTEXPR unsigned long long operator()(T) {
+    handler_.on_error("width is not integer");
+    return 0;
+  }
+
+ private:
+  ErrorHandler& handler_;
+};
+
+template <typename ErrorHandler> class precision_checker {
+ public:
+  explicit FMT_CONSTEXPR precision_checker(ErrorHandler& eh) : handler_(eh) {}
+
+  template <typename T, FMT_ENABLE_IF(is_integer<T>::value)>
+  FMT_CONSTEXPR unsigned long long operator()(T value) {
+    if (is_negative(value)) handler_.on_error("negative precision");
+    return static_cast<unsigned long long>(value);
+  }
+
+  template <typename T, FMT_ENABLE_IF(!is_integer<T>::value)>
+  FMT_CONSTEXPR unsigned long long operator()(T) {
+    handler_.on_error("precision is not integer");
+    return 0;
+  }
+
+ private:
+  ErrorHandler& handler_;
+};
+
+// A format specifier handler that sets fields in basic_format_specs.
+template <typename Char> class specs_setter {
+ public:
+  explicit FMT_CONSTEXPR specs_setter(basic_format_specs<Char>& specs)
+      : specs_(specs) {}
+
+  FMT_CONSTEXPR specs_setter(const specs_setter& other)
+      : specs_(other.specs_) {}
+
+  FMT_CONSTEXPR void on_align(align_t align) { specs_.align = align; }
+  FMT_CONSTEXPR void on_fill(basic_string_view<Char> fill) {
+    specs_.fill = fill;
+  }
+  FMT_CONSTEXPR void on_plus() { specs_.sign = sign::plus; }
+  FMT_CONSTEXPR void on_minus() { specs_.sign = sign::minus; }
+  FMT_CONSTEXPR void on_space() { specs_.sign = sign::space; }
+  FMT_CONSTEXPR void on_hash() { specs_.alt = true; }
+
+  FMT_CONSTEXPR void on_zero() {
+    specs_.align = align::numeric;
+    specs_.fill[0] = Char('0');
+  }
+
+  FMT_CONSTEXPR void on_width(int width) { specs_.width = width; }
+  FMT_CONSTEXPR void on_precision(int precision) {
+    specs_.precision = precision;
+  }
+  FMT_CONSTEXPR void end_precision() {}
+
+  FMT_CONSTEXPR void on_type(Char type) {
+    specs_.type = static_cast<char>(type);
+  }
+
+ protected:
+  basic_format_specs<Char>& specs_;
+};
+
+template <typename ErrorHandler> class numeric_specs_checker {
+ public:
+  FMT_CONSTEXPR numeric_specs_checker(ErrorHandler& eh, detail::type arg_type)
+      : error_handler_(eh), arg_type_(arg_type) {}
+
+  FMT_CONSTEXPR void require_numeric_argument() {
+    if (!is_arithmetic_type(arg_type_))
+      error_handler_.on_error("format specifier requires numeric argument");
+  }
+
+  FMT_CONSTEXPR void check_sign() {
+    require_numeric_argument();
+    if (is_integral_type(arg_type_) && arg_type_ != type::int_type &&
+        arg_type_ != type::long_long_type && arg_type_ != type::char_type) {
+      error_handler_.on_error("format specifier requires signed argument");
+    }
+  }
+
+  FMT_CONSTEXPR void check_precision() {
+    if (is_integral_type(arg_type_) || arg_type_ == type::pointer_type)
+      error_handler_.on_error("precision not allowed for this argument type");
+  }
+
+ private:
+  ErrorHandler& error_handler_;
+  detail::type arg_type_;
+};
+
+// A format specifier handler that checks if specifiers are consistent with the
+// argument type.
+template <typename Handler> class specs_checker : public Handler {
+ private:
+  numeric_specs_checker<Handler> checker_;
+
+  // Suppress an MSVC warning about using this in initializer list.
+  FMT_CONSTEXPR Handler& error_handler() { return *this; }
+
+ public:
+  FMT_CONSTEXPR specs_checker(const Handler& handler, detail::type arg_type)
+      : Handler(handler), checker_(error_handler(), arg_type) {}
+
+  FMT_CONSTEXPR specs_checker(const specs_checker& other)
+      : Handler(other), checker_(error_handler(), other.arg_type_) {}
+
+  FMT_CONSTEXPR void on_align(align_t align) {
+    if (align == align::numeric) checker_.require_numeric_argument();
+    Handler::on_align(align);
+  }
+
+  FMT_CONSTEXPR void on_plus() {
+    checker_.check_sign();
+    Handler::on_plus();
+  }
+
+  FMT_CONSTEXPR void on_minus() {
+    checker_.check_sign();
+    Handler::on_minus();
+  }
+
+  FMT_CONSTEXPR void on_space() {
+    checker_.check_sign();
+    Handler::on_space();
+  }
+
+  FMT_CONSTEXPR void on_hash() {
+    checker_.require_numeric_argument();
+    Handler::on_hash();
+  }
+
+  FMT_CONSTEXPR void on_zero() {
+    checker_.require_numeric_argument();
+    Handler::on_zero();
+  }
+
+  FMT_CONSTEXPR void end_precision() { checker_.check_precision(); }
+};
+
+template <template <typename> class Handler, typename FormatArg,
+          typename ErrorHandler>
+FMT_CONSTEXPR int get_dynamic_spec(FormatArg arg, ErrorHandler eh) {
+  unsigned long long value = visit_format_arg(Handler<ErrorHandler>(eh), arg);
+  if (value > to_unsigned(max_value<int>())) eh.on_error("number is too big");
+  return static_cast<int>(value);
+}
+
+struct auto_id {};
+
+template <typename Context, typename ID>
+FMT_CONSTEXPR typename Context::format_arg get_arg(Context& ctx, ID id) {
+  auto arg = ctx.arg(id);
+  if (!arg) ctx.on_error("argument not found");
+  return arg;
+}
+
+// The standard format specifier handler with checking.
+template <typename ParseContext, typename Context>
+class specs_handler : public specs_setter<typename Context::char_type> {
+ public:
+  using char_type = typename Context::char_type;
+
+  FMT_CONSTEXPR specs_handler(basic_format_specs<char_type>& specs,
+                              ParseContext& parse_ctx, Context& ctx)
+      : specs_setter<char_type>(specs),
+        parse_context_(parse_ctx),
+        context_(ctx) {}
+
+  template <typename Id> FMT_CONSTEXPR void on_dynamic_width(Id arg_id) {
+    this->specs_.width = get_dynamic_spec<width_checker>(
+        get_arg(arg_id), context_.error_handler());
+  }
+
+  template <typename Id> FMT_CONSTEXPR void on_dynamic_precision(Id arg_id) {
+    this->specs_.precision = get_dynamic_spec<precision_checker>(
+        get_arg(arg_id), context_.error_handler());
+  }
+
+  void on_error(const char* message) { context_.on_error(message); }
+
+ private:
+  // This is only needed for compatibility with gcc 4.4.
+  using format_arg = typename Context::format_arg;
+
+  FMT_CONSTEXPR format_arg get_arg(auto_id) {
+    return detail::get_arg(context_, parse_context_.next_arg_id());
+  }
+
+  FMT_CONSTEXPR format_arg get_arg(int arg_id) {
+    parse_context_.check_arg_id(arg_id);
+    return detail::get_arg(context_, arg_id);
+  }
+
+  FMT_CONSTEXPR format_arg get_arg(basic_string_view<char_type> arg_id) {
+    parse_context_.check_arg_id(arg_id);
+    return detail::get_arg(context_, arg_id);
+  }
+
+  ParseContext& parse_context_;
+  Context& context_;
+};
+
+enum class arg_id_kind { none, index, name };
+
+// An argument reference.
+template <typename Char> struct arg_ref {
+  FMT_CONSTEXPR arg_ref() : kind(arg_id_kind::none), val() {}
+
+  FMT_CONSTEXPR explicit arg_ref(int index)
+      : kind(arg_id_kind::index), val(index) {}
+  FMT_CONSTEXPR explicit arg_ref(basic_string_view<Char> name)
+      : kind(arg_id_kind::name), val(name) {}
+
+  FMT_CONSTEXPR arg_ref& operator=(int idx) {
+    kind = arg_id_kind::index;
+    val.index = idx;
+    return *this;
+  }
+
+  arg_id_kind kind;
+  union value {
+    FMT_CONSTEXPR value(int id = 0) : index{id} {}
+    FMT_CONSTEXPR value(basic_string_view<Char> n) : name(n) {}
+
+    int index;
+    basic_string_view<Char> name;
+  } val;
+};
+
+// Format specifiers with width and precision resolved at formatting rather
+// than parsing time to allow re-using the same parsed specifiers with
+// different sets of arguments (precompilation of format strings).
+template <typename Char>
+struct dynamic_format_specs : basic_format_specs<Char> {
+  arg_ref<Char> width_ref;
+  arg_ref<Char> precision_ref;
+};
+
+// Format spec handler that saves references to arguments representing dynamic
+// width and precision to be resolved at formatting time.
+template <typename ParseContext>
+class dynamic_specs_handler
+    : public specs_setter<typename ParseContext::char_type> {
+ public:
+  using char_type = typename ParseContext::char_type;
+
+  FMT_CONSTEXPR dynamic_specs_handler(dynamic_format_specs<char_type>& specs,
+                                      ParseContext& ctx)
+      : specs_setter<char_type>(specs), specs_(specs), context_(ctx) {}
+
+  FMT_CONSTEXPR dynamic_specs_handler(const dynamic_specs_handler& other)
+      : specs_setter<char_type>(other),
+        specs_(other.specs_),
+        context_(other.context_) {}
+
+  template <typename Id> FMT_CONSTEXPR void on_dynamic_width(Id arg_id) {
+    specs_.width_ref = make_arg_ref(arg_id);
+  }
+
+  template <typename Id> FMT_CONSTEXPR void on_dynamic_precision(Id arg_id) {
+    specs_.precision_ref = make_arg_ref(arg_id);
+  }
+
+  FMT_CONSTEXPR void on_error(const char* message) {
+    context_.on_error(message);
+  }
+
+ private:
+  using arg_ref_type = arg_ref<char_type>;
+
+  FMT_CONSTEXPR arg_ref_type make_arg_ref(int arg_id) {
+    context_.check_arg_id(arg_id);
+    return arg_ref_type(arg_id);
+  }
+
+  FMT_CONSTEXPR arg_ref_type make_arg_ref(auto_id) {
+    return arg_ref_type(context_.next_arg_id());
+  }
+
+  FMT_CONSTEXPR arg_ref_type make_arg_ref(basic_string_view<char_type> arg_id) {
+    context_.check_arg_id(arg_id);
+    basic_string_view<char_type> format_str(
+        context_.begin(), to_unsigned(context_.end() - context_.begin()));
+    return arg_ref_type(arg_id);
+  }
+
+  dynamic_format_specs<char_type>& specs_;
+  ParseContext& context_;
+};
+
+template <typename Char, typename IDHandler>
+FMT_CONSTEXPR const Char* parse_arg_id(const Char* begin, const Char* end,
+                                       IDHandler&& handler) {
+  FMT_ASSERT(begin != end, "");
+  Char c = *begin;
+  if (c == '}' || c == ':') {
+    handler();
+    return begin;
+  }
+  if (c >= '0' && c <= '9') {
+    int index = 0;
+    if (c != '0')
+      index = parse_nonnegative_int(begin, end, handler);
+    else
+      ++begin;
+    if (begin == end || (*begin != '}' && *begin != ':'))
+      handler.on_error("invalid format string");
+    else
+      handler(index);
+    return begin;
+  }
+  if (!is_name_start(c)) {
+    handler.on_error("invalid format string");
+    return begin;
+  }
+  auto it = begin;
+  do {
+    ++it;
+  } while (it != end && (is_name_start(c = *it) || ('0' <= c && c <= '9')));
+  handler(basic_string_view<Char>(begin, to_unsigned(it - begin)));
+  return it;
+}
+
+// Adapts SpecHandler to IDHandler API for dynamic width.
+template <typename SpecHandler, typename Char> struct width_adapter {
+  explicit FMT_CONSTEXPR width_adapter(SpecHandler& h) : handler(h) {}
+
+  FMT_CONSTEXPR void operator()() { handler.on_dynamic_width(auto_id()); }
+  FMT_CONSTEXPR void operator()(int id) { handler.on_dynamic_width(id); }
+  FMT_CONSTEXPR void operator()(basic_string_view<Char> id) {
+    handler.on_dynamic_width(id);
+  }
+
+  FMT_CONSTEXPR void on_error(const char* message) {
+    handler.on_error(message);
+  }
+
+  SpecHandler& handler;
+};
+
+// Adapts SpecHandler to IDHandler API for dynamic precision.
+template <typename SpecHandler, typename Char> struct precision_adapter {
+  explicit FMT_CONSTEXPR precision_adapter(SpecHandler& h) : handler(h) {}
+
+  FMT_CONSTEXPR void operator()() { handler.on_dynamic_precision(auto_id()); }
+  FMT_CONSTEXPR void operator()(int id) { handler.on_dynamic_precision(id); }
+  FMT_CONSTEXPR void operator()(basic_string_view<Char> id) {
+    handler.on_dynamic_precision(id);
+  }
+
+  FMT_CONSTEXPR void on_error(const char* message) {
+    handler.on_error(message);
+  }
+
+  SpecHandler& handler;
+};
+
+template <typename Char>
+FMT_CONSTEXPR const Char* next_code_point(const Char* begin, const Char* end) {
+  if (const_check(sizeof(Char) != 1) || (*begin & 0x80) == 0) return begin + 1;
+  do {
+    ++begin;
+  } while (begin != end && (*begin & 0xc0) == 0x80);
+  return begin;
+}
+
+// Parses fill and alignment.
+template <typename Char, typename Handler>
+FMT_CONSTEXPR const Char* parse_align(const Char* begin, const Char* end,
+                                      Handler&& handler) {
+  FMT_ASSERT(begin != end, "");
+  auto align = align::none;
+  auto p = next_code_point(begin, end);
+  if (p == end) p = begin;
+  for (;;) {
+    switch (static_cast<char>(*p)) {
+    case '<':
+      align = align::left;
+      break;
+    case '>':
+      align = align::right;
+      break;
+#if FMT_DEPRECATED_NUMERIC_ALIGN
+    case '=':
+      align = align::numeric;
+      break;
+#endif
+    case '^':
+      align = align::center;
+      break;
+    }
+    if (align != align::none) {
+      if (p != begin) {
+        auto c = *begin;
+        if (c == '{')
+          return handler.on_error("invalid fill character '{'"), begin;
+        handler.on_fill(basic_string_view<Char>(begin, to_unsigned(p - begin)));
+        begin = p + 1;
+      } else
+        ++begin;
+      handler.on_align(align);
+      break;
+    } else if (p == begin) {
+      break;
+    }
+    p = begin;
+  }
+  return begin;
+}
+
+template <typename Char, typename Handler>
+FMT_CONSTEXPR const Char* parse_width(const Char* begin, const Char* end,
+                                      Handler&& handler) {
+  FMT_ASSERT(begin != end, "");
+  if ('0' <= *begin && *begin <= '9') {
+    handler.on_width(parse_nonnegative_int(begin, end, handler));
+  } else if (*begin == '{') {
+    ++begin;
+    if (begin != end)
+      begin = parse_arg_id(begin, end, width_adapter<Handler, Char>(handler));
+    if (begin == end || *begin != '}')
+      return handler.on_error("invalid format string"), begin;
+    ++begin;
+  }
+  return begin;
+}
+
+template <typename Char, typename Handler>
+FMT_CONSTEXPR const Char* parse_precision(const Char* begin, const Char* end,
+                                          Handler&& handler) {
+  ++begin;
+  auto c = begin != end ? *begin : Char();
+  if ('0' <= c && c <= '9') {
+    handler.on_precision(parse_nonnegative_int(begin, end, handler));
+  } else if (c == '{') {
+    ++begin;
+    if (begin != end) {
+      begin =
+          parse_arg_id(begin, end, precision_adapter<Handler, Char>(handler));
+    }
+    if (begin == end || *begin++ != '}')
+      return handler.on_error("invalid format string"), begin;
+  } else {
+    return handler.on_error("missing precision specifier"), begin;
+  }
+  handler.end_precision();
+  return begin;
+}
+
+// Parses standard format specifiers and sends notifications about parsed
+// components to handler.
+template <typename Char, typename SpecHandler>
+FMT_CONSTEXPR const Char* parse_format_specs(const Char* begin, const Char* end,
+                                             SpecHandler&& handler) {
+  if (begin == end || *begin == '}') return begin;
+
+  begin = parse_align(begin, end, handler);
+  if (begin == end) return begin;
+
+  // Parse sign.
+  switch (static_cast<char>(*begin)) {
+  case '+':
+    handler.on_plus();
+    ++begin;
+    break;
+  case '-':
+    handler.on_minus();
+    ++begin;
+    break;
+  case ' ':
+    handler.on_space();
+    ++begin;
+    break;
+  }
+  if (begin == end) return begin;
+
+  if (*begin == '#') {
+    handler.on_hash();
+    if (++begin == end) return begin;
+  }
+
+  // Parse zero flag.
+  if (*begin == '0') {
+    handler.on_zero();
+    if (++begin == end) return begin;
+  }
+
+  begin = parse_width(begin, end, handler);
+  if (begin == end) return begin;
+
+  // Parse precision.
+  if (*begin == '.') {
+    begin = parse_precision(begin, end, handler);
+  }
+
+  // Parse type.
+  if (begin != end && *begin != '}') handler.on_type(*begin++);
+  return begin;
+}
+
+// Return the result via the out param to workaround gcc bug 77539.
+template <bool IS_CONSTEXPR, typename T, typename Ptr = const T*>
+FMT_CONSTEXPR bool find(Ptr first, Ptr last, T value, Ptr& out) {
+  for (out = first; out != last; ++out) {
+    if (*out == value) return true;
+  }
+  return false;
+}
+
+template <>
+inline bool find<false, char>(const char* first, const char* last, char value,
+                              const char*& out) {
+  out = static_cast<const char*>(
+      std::memchr(first, value, detail::to_unsigned(last - first)));
+  return out != nullptr;
+}
+
+template <typename Handler, typename Char> struct id_adapter {
+  Handler& handler;
+  int arg_id;
+
+  FMT_CONSTEXPR void operator()() { arg_id = handler.on_arg_id(); }
+  FMT_CONSTEXPR void operator()(int id) { arg_id = handler.on_arg_id(id); }
+  FMT_CONSTEXPR void operator()(basic_string_view<Char> id) {
+    arg_id = handler.on_arg_id(id);
+  }
+  FMT_CONSTEXPR void on_error(const char* message) {
+    handler.on_error(message);
+  }
+};
+
+template <typename Char, typename Handler>
+FMT_CONSTEXPR const Char* parse_replacement_field(const Char* begin,
+                                                  const Char* end,
+                                                  Handler&& handler) {
+  ++begin;
+  if (begin == end) return handler.on_error("invalid format string"), end;
+  if (static_cast<char>(*begin) == '}') {
+    handler.on_replacement_field(handler.on_arg_id(), begin);
+  } else if (*begin == '{') {
+    handler.on_text(begin, begin + 1);
+  } else {
+    auto adapter = id_adapter<Handler, Char>{handler, 0};
+    begin = parse_arg_id(begin, end, adapter);
+    Char c = begin != end ? *begin : Char();
+    if (c == '}') {
+      handler.on_replacement_field(adapter.arg_id, begin);
+    } else if (c == ':') {
+      begin = handler.on_format_specs(adapter.arg_id, begin + 1, end);
+      if (begin == end || *begin != '}')
+        return handler.on_error("unknown format specifier"), end;
+    } else {
+      return handler.on_error("missing '}' in format string"), end;
+    }
+  }
+  return begin + 1;
+}
+
+template <bool IS_CONSTEXPR, typename Char, typename Handler>
+FMT_CONSTEXPR_DECL FMT_INLINE void parse_format_string(
+    basic_string_view<Char> format_str, Handler&& handler) {
+  auto begin = format_str.data();
+  auto end = begin + format_str.size();
+  if (end - begin < 32) {
+    // Use a simple loop instead of memchr for small strings.
+    const Char* p = begin;
+    while (p != end) {
+      auto c = *p++;
+      if (c == '{') {
+        handler.on_text(begin, p - 1);
+        begin = p = parse_replacement_field(p - 1, end, handler);
+      } else if (c == '}') {
+        if (p == end || *p != '}')
+          return handler.on_error("unmatched '}' in format string");
+        handler.on_text(begin, p);
+        begin = ++p;
+      }
+    }
+    handler.on_text(begin, end);
+    return;
+  }
+  struct writer {
+    FMT_CONSTEXPR void operator()(const Char* begin, const Char* end) {
+      if (begin == end) return;
+      for (;;) {
+        const Char* p = nullptr;
+        if (!find<IS_CONSTEXPR>(begin, end, '}', p))
+          return handler_.on_text(begin, end);
+        ++p;
+        if (p == end || *p != '}')
+          return handler_.on_error("unmatched '}' in format string");
+        handler_.on_text(begin, p);
+        begin = p + 1;
+      }
+    }
+    Handler& handler_;
+  } write{handler};
+  while (begin != end) {
+    // Doing two passes with memchr (one for '{' and another for '}') is up to
+    // 2.5x faster than the naive one-pass implementation on big format strings.
+    const Char* p = begin;
+    if (*begin != '{' && !find<IS_CONSTEXPR>(begin + 1, end, '{', p))
+      return write(begin, end);
+    write(begin, p);
+    begin = parse_replacement_field(p, end, handler);
+  }
+}
+
+template <typename T, typename ParseContext>
+FMT_CONSTEXPR const typename ParseContext::char_type* parse_format_specs(
+    ParseContext& ctx) {
+  using char_type = typename ParseContext::char_type;
+  using context = buffer_context<char_type>;
+  using mapped_type =
+      conditional_t<detail::mapped_type_constant<T, context>::value !=
+                        type::custom_type,
+                    decltype(arg_mapper<context>().map(std::declval<T>())), T>;
+  auto f = conditional_t<has_formatter<mapped_type, context>::value,
+                         formatter<mapped_type, char_type>,
+                         detail::fallback_formatter<T, char_type>>();
+  return f.parse(ctx);
+}
+
+template <typename ArgFormatter, typename Char, typename Context>
+struct format_handler : detail::error_handler {
+  basic_format_parse_context<Char> parse_context;
+  Context context;
+
+  format_handler(typename ArgFormatter::iterator out,
+                 basic_string_view<Char> str,
+                 basic_format_args<Context> format_args, detail::locale_ref loc)
+      : parse_context(str), context(out, format_args, loc) {}
+
+  void on_text(const Char* begin, const Char* end) {
+    auto size = to_unsigned(end - begin);
+    auto out = context.out();
+    auto&& it = reserve(out, size);
+    it = std::copy_n(begin, size, it);
+    context.advance_to(out);
+  }
+
+  int on_arg_id() { return parse_context.next_arg_id(); }
+  int on_arg_id(int id) { return parse_context.check_arg_id(id), id; }
+  int on_arg_id(basic_string_view<Char> id) {
+    int arg_id = context.arg_id(id);
+    if (arg_id < 0) on_error("argument not found");
+    return arg_id;
+  }
+
+  FMT_INLINE void on_replacement_field(int id, const Char*) {
+    auto arg = get_arg(context, id);
+    context.advance_to(visit_format_arg(
+        default_arg_formatter<typename ArgFormatter::iterator, Char>{
+            context.out(), context.args(), context.locale()},
+        arg));
+  }
+
+  const Char* on_format_specs(int id, const Char* begin, const Char* end) {
+    advance_to(parse_context, begin);
+    auto arg = get_arg(context, id);
+    custom_formatter<Context> f(parse_context, context);
+    if (visit_format_arg(f, arg)) return parse_context.begin();
+    basic_format_specs<Char> specs;
+    using parse_context_t = basic_format_parse_context<Char>;
+    specs_checker<specs_handler<parse_context_t, Context>> handler(
+        specs_handler<parse_context_t, Context>(specs, parse_context, context),
+        arg.type());
+    begin = parse_format_specs(begin, end, handler);
+    if (begin == end || *begin != '}') on_error("missing '}' in format string");
+    advance_to(parse_context, begin);
+    context.advance_to(
+        visit_format_arg(ArgFormatter(context, &parse_context, &specs), arg));
+    return begin;
+  }
+};
+
+// A parse context with extra argument id checks. It is only used at compile
+// time because adding checks at runtime would introduce substantial overhead
+// and would be redundant since argument ids are checked when arguments are
+// retrieved anyway.
+template <typename Char, typename ErrorHandler = error_handler>
+class compile_parse_context
+    : public basic_format_parse_context<Char, ErrorHandler> {
+ private:
+  int num_args_;
+  using base = basic_format_parse_context<Char, ErrorHandler>;
+
+ public:
+  explicit FMT_CONSTEXPR compile_parse_context(
+      basic_string_view<Char> format_str, int num_args = max_value<int>(),
+      ErrorHandler eh = {})
+      : base(format_str, eh), num_args_(num_args) {}
+
+  FMT_CONSTEXPR int next_arg_id() {
+    int id = base::next_arg_id();
+    if (id >= num_args_) this->on_error("argument not found");
+    return id;
+  }
+
+  FMT_CONSTEXPR void check_arg_id(int id) {
+    base::check_arg_id(id);
+    if (id >= num_args_) this->on_error("argument not found");
+  }
+  using base::check_arg_id;
+};
+
+template <typename Char, typename ErrorHandler, typename... Args>
+class format_string_checker {
+ public:
+  explicit FMT_CONSTEXPR format_string_checker(
+      basic_string_view<Char> format_str, ErrorHandler eh)
+      : context_(format_str, num_args, eh),
+        parse_funcs_{&parse_format_specs<Args, parse_context_type>...} {}
+
+  FMT_CONSTEXPR void on_text(const Char*, const Char*) {}
+
+  FMT_CONSTEXPR int on_arg_id() { return context_.next_arg_id(); }
+  FMT_CONSTEXPR int on_arg_id(int id) { return context_.check_arg_id(id), id; }
+  FMT_CONSTEXPR int on_arg_id(basic_string_view<Char>) {
+    on_error("compile-time checks don't support named arguments");
+    return 0;
+  }
+
+  FMT_CONSTEXPR void on_replacement_field(int, const Char*) {}
+
+  FMT_CONSTEXPR const Char* on_format_specs(int id, const Char* begin,
+                                            const Char*) {
+    advance_to(context_, begin);
+    return id < num_args ? parse_funcs_[id](context_) : begin;
+  }
+
+  FMT_CONSTEXPR void on_error(const char* message) {
+    context_.on_error(message);
+  }
+
+ private:
+  using parse_context_type = compile_parse_context<Char, ErrorHandler>;
+  enum { num_args = sizeof...(Args) };
+
+  // Format specifier parsing function.
+  using parse_func = const Char* (*)(parse_context_type&);
+
+  parse_context_type context_;
+  parse_func parse_funcs_[num_args > 0 ? num_args : 1];
+};
+
+// Converts string literals to basic_string_view.
+template <typename Char, size_t N>
+FMT_CONSTEXPR basic_string_view<Char> compile_string_to_view(
+    const Char (&s)[N]) {
+  // Remove trailing null character if needed. Won't be present if this is used
+  // with raw character array (i.e. not defined as a string).
+  return {s,
+          N - ((std::char_traits<Char>::to_int_type(s[N - 1]) == 0) ? 1 : 0)};
+}
+
+// Converts string_view to basic_string_view.
+template <typename Char>
+FMT_CONSTEXPR basic_string_view<Char> compile_string_to_view(
+    const std_string_view<Char>& s) {
+  return {s.data(), s.size()};
+}
+
+#define FMT_STRING_IMPL(s, base)                                  \
+  [] {                                                            \
+    /* Use a macro-like name to avoid shadowing warnings. */      \
+    struct FMT_COMPILE_STRING : base {                            \
+      using char_type = fmt::remove_cvref_t<decltype(s[0])>;      \
+      FMT_MAYBE_UNUSED FMT_CONSTEXPR                              \
+      operator fmt::basic_string_view<char_type>() const {        \
+        return fmt::detail::compile_string_to_view<char_type>(s); \
+      }                                                           \
+    };                                                            \
+    return FMT_COMPILE_STRING();                                  \
+  }()
+
+/**
+  \rst
+  Constructs a compile-time format string from a string literal *s*.
+
+  **Example**::
+
+    // A compile-time error because 'd' is an invalid specifier for strings.
+    std::string s = fmt::format(FMT_STRING("{:d}"), "foo");
+  \endrst
+ */
+#define FMT_STRING(s) FMT_STRING_IMPL(s, fmt::compile_string)
+
+template <typename... Args, typename S,
+          enable_if_t<(is_compile_string<S>::value), int>>
+void check_format_string(S format_str) {
+  FMT_CONSTEXPR_DECL auto s = to_string_view(format_str);
+  using checker = format_string_checker<typename S::char_type, error_handler,
+                                        remove_cvref_t<Args>...>;
+  FMT_CONSTEXPR_DECL bool invalid_format =
+      (parse_format_string<true>(s, checker(s, {})), true);
+  (void)invalid_format;
+}
+
+template <template <typename> class Handler, typename Context>
+void handle_dynamic_spec(int& value, arg_ref<typename Context::char_type> ref,
+                         Context& ctx) {
+  switch (ref.kind) {
+  case arg_id_kind::none:
+    break;
+  case arg_id_kind::index:
+    value = detail::get_dynamic_spec<Handler>(ctx.arg(ref.val.index),
+                                              ctx.error_handler());
+    break;
+  case arg_id_kind::name:
+    value = detail::get_dynamic_spec<Handler>(ctx.arg(ref.val.name),
+                                              ctx.error_handler());
+    break;
+  }
+}
+
+using format_func = void (*)(detail::buffer<char>&, int, string_view);
+
+FMT_API void format_error_code(buffer<char>& out, int error_code,
+                               string_view message) FMT_NOEXCEPT;
+
+FMT_API void report_error(format_func func, int error_code,
+                          string_view message) FMT_NOEXCEPT;
+
+/** The default argument formatter. */
+template <typename OutputIt, typename Char>
+class arg_formatter : public arg_formatter_base<OutputIt, Char> {
+ private:
+  using char_type = Char;
+  using base = arg_formatter_base<OutputIt, Char>;
+  using context_type = basic_format_context<OutputIt, Char>;
+
+  context_type& ctx_;
+  basic_format_parse_context<char_type>* parse_ctx_;
+  const Char* ptr_;
+
+ public:
+  using iterator = typename base::iterator;
+  using format_specs = typename base::format_specs;
+
+  /**
+    \rst
+    Constructs an argument formatter object.
+    *ctx* is a reference to the formatting context,
+    *specs* contains format specifier information for standard argument types.
+    \endrst
+   */
+  explicit arg_formatter(
+      context_type& ctx,
+      basic_format_parse_context<char_type>* parse_ctx = nullptr,
+      format_specs* specs = nullptr, const Char* ptr = nullptr)
+      : base(ctx.out(), specs, ctx.locale()),
+        ctx_(ctx),
+        parse_ctx_(parse_ctx),
+        ptr_(ptr) {}
+
+  using base::operator();
+
+  /** Formats an argument of a user-defined type. */
+  iterator operator()(typename basic_format_arg<context_type>::handle handle) {
+    if (ptr_) advance_to(*parse_ctx_, ptr_);
+    handle.format(*parse_ctx_, ctx_);
+    return ctx_.out();
+  }
+};
+}  // namespace detail
+
+template <typename OutputIt, typename Char>
+using arg_formatter FMT_DEPRECATED_ALIAS =
+  detail::arg_formatter<OutputIt, Char>;
+
+/**
+ An error returned by an operating system or a language runtime,
+ for example a file opening error.
+*/
+FMT_CLASS_API
+class FMT_API system_error : public std::runtime_error {
+ private:
+  void init(int err_code, string_view format_str, format_args args);
+
+ protected:
+  int error_code_;
+
+  system_error() : std::runtime_error(""), error_code_(0) {}
+
+ public:
+  /**
+   \rst
+   Constructs a :class:`fmt::system_error` object with a description
+   formatted with `fmt::format_system_error`. *message* and additional
+   arguments passed into the constructor are formatted similarly to
+   `fmt::format`.
+
+   **Example**::
+
+     // This throws a system_error with the description
+     //   cannot open file 'madeup': No such file or directory
+     // or similar (system message may vary).
+     const char *filename = "madeup";
+     std::FILE *file = std::fopen(filename, "r");
+     if (!file)
+       throw fmt::system_error(errno, "cannot open file '{}'", filename);
+   \endrst
+  */
+  template <typename... Args>
+  system_error(int error_code, string_view message, const Args&... args)
+      : std::runtime_error("") {
+    init(error_code, message, make_format_args(args...));
+  }
+  system_error(const system_error&) = default;
+  system_error& operator=(const system_error&) = default;
+  system_error(system_error&&) = default;
+  system_error& operator=(system_error&&) = default;
+  ~system_error() FMT_NOEXCEPT FMT_OVERRIDE;
+
+  int error_code() const { return error_code_; }
+};
+
+/**
+  \rst
+  Formats an error returned by an operating system or a language runtime,
+  for example a file opening error, and writes it to *out* in the following
+  form:
+
+  .. parsed-literal::
+     *<message>*: *<system-message>*
+
+  where *<message>* is the passed message and *<system-message>* is
+  the system message corresponding to the error code.
+  *error_code* is a system error code as given by ``errno``.
+  If *error_code* is not a valid error code such as -1, the system message
+  may look like "Unknown error -1" and is platform-dependent.
+  \endrst
+ */
+FMT_API void format_system_error(detail::buffer<char>& out, int error_code,
+                                 string_view message) FMT_NOEXCEPT;
+
+// Reports a system error without throwing an exception.
+// Can be used to report errors from destructors.
+FMT_API void report_system_error(int error_code,
+                                 string_view message) FMT_NOEXCEPT;
+
+/** Fast integer formatter. */
+class format_int {
+ private:
+  // Buffer should be large enough to hold all digits (digits10 + 1),
+  // a sign and a null character.
+  enum { buffer_size = std::numeric_limits<unsigned long long>::digits10 + 3 };
+  mutable char buffer_[buffer_size];
+  char* str_;
+
+  template <typename UInt> char* format_unsigned(UInt value) {
+    auto n = static_cast<detail::uint32_or_64_or_128_t<UInt>>(value);
+    return detail::format_decimal(buffer_, n, buffer_size - 1).begin;
+  }
+
+  template <typename Int> char* format_signed(Int value) {
+    auto abs_value = static_cast<detail::uint32_or_64_or_128_t<Int>>(value);
+    bool negative = value < 0;
+    if (negative) abs_value = 0 - abs_value;
+    auto begin = format_unsigned(abs_value);
+    if (negative) *--begin = '-';
+    return begin;
+  }
+
+ public:
+  explicit format_int(int value) : str_(format_signed(value)) {}
+  explicit format_int(long value) : str_(format_signed(value)) {}
+  explicit format_int(long long value) : str_(format_signed(value)) {}
+  explicit format_int(unsigned value) : str_(format_unsigned(value)) {}
+  explicit format_int(unsigned long value) : str_(format_unsigned(value)) {}
+  explicit format_int(unsigned long long value)
+      : str_(format_unsigned(value)) {}
+
+  /** Returns the number of characters written to the output buffer. */
+  size_t size() const {
+    return detail::to_unsigned(buffer_ - str_ + buffer_size - 1);
+  }
+
+  /**
+    Returns a pointer to the output buffer content. No terminating null
+    character is appended.
+   */
+  const char* data() const { return str_; }
+
+  /**
+    Returns a pointer to the output buffer content with terminating null
+    character appended.
+   */
+  const char* c_str() const {
+    buffer_[buffer_size - 1] = '\0';
+    return str_;
+  }
+
+  /**
+    \rst
+    Returns the content of the output buffer as an ``std::string``.
+    \endrst
+   */
+  std::string str() const { return std::string(str_, size()); }
+};
+
+// A formatter specialization for the core types corresponding to detail::type
+// constants.
+template <typename T, typename Char>
+struct formatter<T, Char,
+                 enable_if_t<detail::type_constant<T, Char>::value !=
+                             detail::type::custom_type>> {
+  FMT_CONSTEXPR formatter() = default;
+
+  // Parses format specifiers stopping either at the end of the range or at the
+  // terminating '}'.
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    using handler_type = detail::dynamic_specs_handler<ParseContext>;
+    auto type = detail::type_constant<T, Char>::value;
+    detail::specs_checker<handler_type> handler(handler_type(specs_, ctx),
+                                                type);
+    auto it = parse_format_specs(ctx.begin(), ctx.end(), handler);
+    auto eh = ctx.error_handler();
+    switch (type) {
+    case detail::type::none_type:
+      FMT_ASSERT(false, "invalid argument type");
+      break;
+    case detail::type::int_type:
+    case detail::type::uint_type:
+    case detail::type::long_long_type:
+    case detail::type::ulong_long_type:
+    case detail::type::int128_type:
+    case detail::type::uint128_type:
+    case detail::type::bool_type:
+      handle_int_type_spec(specs_.type,
+                           detail::int_type_checker<decltype(eh)>(eh));
+      break;
+    case detail::type::char_type:
+      handle_char_specs(
+          &specs_, detail::char_specs_checker<decltype(eh)>(specs_.type, eh));
+      break;
+    case detail::type::float_type:
+      if (detail::const_check(FMT_USE_FLOAT))
+        detail::parse_float_type_spec(specs_, eh);
+      else
+        FMT_ASSERT(false, "float support disabled");
+      break;
+    case detail::type::double_type:
+      if (detail::const_check(FMT_USE_DOUBLE))
+        detail::parse_float_type_spec(specs_, eh);
+      else
+        FMT_ASSERT(false, "double support disabled");
+      break;
+    case detail::type::long_double_type:
+      if (detail::const_check(FMT_USE_LONG_DOUBLE))
+        detail::parse_float_type_spec(specs_, eh);
+      else
+        FMT_ASSERT(false, "long double support disabled");
+      break;
+    case detail::type::cstring_type:
+      detail::handle_cstring_type_spec(
+          specs_.type, detail::cstring_type_checker<decltype(eh)>(eh));
+      break;
+    case detail::type::string_type:
+      detail::check_string_type_spec(specs_.type, eh);
+      break;
+    case detail::type::pointer_type:
+      detail::check_pointer_type_spec(specs_.type, eh);
+      break;
+    case detail::type::custom_type:
+      // Custom format specifiers should be checked in parse functions of
+      // formatter specializations.
+      break;
+    }
+    return it;
+  }
+
+  template <typename FormatContext>
+  auto format(const T& val, FormatContext& ctx) -> decltype(ctx.out()) {
+    detail::handle_dynamic_spec<detail::width_checker>(specs_.width,
+                                                       specs_.width_ref, ctx);
+    detail::handle_dynamic_spec<detail::precision_checker>(
+        specs_.precision, specs_.precision_ref, ctx);
+    using af = detail::arg_formatter<typename FormatContext::iterator,
+                                     typename FormatContext::char_type>;
+    return visit_format_arg(af(ctx, nullptr, &specs_),
+                            detail::make_arg<FormatContext>(val));
+  }
+
+ private:
+  detail::dynamic_format_specs<Char> specs_;
+};
+
+#define FMT_FORMAT_AS(Type, Base)                                             \
+  template <typename Char>                                                    \
+  struct formatter<Type, Char> : formatter<Base, Char> {                      \
+    template <typename FormatContext>                                         \
+    auto format(Type const& val, FormatContext& ctx) -> decltype(ctx.out()) { \
+      return formatter<Base, Char>::format(val, ctx);                         \
+    }                                                                         \
+  }
+
+FMT_FORMAT_AS(signed char, int);
+FMT_FORMAT_AS(unsigned char, unsigned);
+FMT_FORMAT_AS(short, int);
+FMT_FORMAT_AS(unsigned short, unsigned);
+FMT_FORMAT_AS(long, long long);
+FMT_FORMAT_AS(unsigned long, unsigned long long);
+FMT_FORMAT_AS(Char*, const Char*);
+FMT_FORMAT_AS(std::basic_string<Char>, basic_string_view<Char>);
+FMT_FORMAT_AS(std::nullptr_t, const void*);
+FMT_FORMAT_AS(detail::std_string_view<Char>, basic_string_view<Char>);
+
+template <typename Char>
+struct formatter<void*, Char> : formatter<const void*, Char> {
+  template <typename FormatContext>
+  auto format(void* val, FormatContext& ctx) -> decltype(ctx.out()) {
+    return formatter<const void*, Char>::format(val, ctx);
+  }
+};
+
+template <typename Char, size_t N>
+struct formatter<Char[N], Char> : formatter<basic_string_view<Char>, Char> {
+  template <typename FormatContext>
+  auto format(const Char* val, FormatContext& ctx) -> decltype(ctx.out()) {
+    return formatter<basic_string_view<Char>, Char>::format(val, ctx);
+  }
+};
+
+// A formatter for types known only at run time such as variant alternatives.
+//
+// Usage:
+//   using variant = std::variant<int, std::string>;
+//   template <>
+//   struct formatter<variant>: dynamic_formatter<> {
+//     void format(buffer &buf, const variant &v, context &ctx) {
+//       visit([&](const auto &val) { format(buf, val, ctx); }, v);
+//     }
+//   };
+template <typename Char = char> class dynamic_formatter {
+ private:
+  struct null_handler : detail::error_handler {
+    void on_align(align_t) {}
+    void on_plus() {}
+    void on_minus() {}
+    void on_space() {}
+    void on_hash() {}
+  };
+
+ public:
+  template <typename ParseContext>
+  auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    format_str_ = ctx.begin();
+    // Checks are deferred to formatting time when the argument type is known.
+    detail::dynamic_specs_handler<ParseContext> handler(specs_, ctx);
+    return parse_format_specs(ctx.begin(), ctx.end(), handler);
+  }
+
+  template <typename T, typename FormatContext>
+  auto format(const T& val, FormatContext& ctx) -> decltype(ctx.out()) {
+    handle_specs(ctx);
+    detail::specs_checker<null_handler> checker(
+        null_handler(), detail::mapped_type_constant<T, FormatContext>::value);
+    checker.on_align(specs_.align);
+    switch (specs_.sign) {
+    case sign::none:
+      break;
+    case sign::plus:
+      checker.on_plus();
+      break;
+    case sign::minus:
+      checker.on_minus();
+      break;
+    case sign::space:
+      checker.on_space();
+      break;
+    }
+    if (specs_.alt) checker.on_hash();
+    if (specs_.precision >= 0) checker.end_precision();
+    using af = detail::arg_formatter<typename FormatContext::iterator,
+                                     typename FormatContext::char_type>;
+    visit_format_arg(af(ctx, nullptr, &specs_),
+                     detail::make_arg<FormatContext>(val));
+    return ctx.out();
+  }
+
+ private:
+  template <typename Context> void handle_specs(Context& ctx) {
+    detail::handle_dynamic_spec<detail::width_checker>(specs_.width,
+                                                       specs_.width_ref, ctx);
+    detail::handle_dynamic_spec<detail::precision_checker>(
+        specs_.precision, specs_.precision_ref, ctx);
+  }
+
+  detail::dynamic_format_specs<Char> specs_;
+  const Char* format_str_;
+};
+
+template <typename Char, typename ErrorHandler>
+FMT_CONSTEXPR void advance_to(
+    basic_format_parse_context<Char, ErrorHandler>& ctx, const Char* p) {
+  ctx.advance_to(ctx.begin() + (p - &*ctx.begin()));
+}
+
+/** Formats arguments and writes the output to the range. */
+template <typename ArgFormatter, typename Char, typename Context>
+typename Context::iterator vformat_to(
+    typename ArgFormatter::iterator out, basic_string_view<Char> format_str,
+    basic_format_args<Context> args,
+    detail::locale_ref loc = detail::locale_ref()) {
+  if (format_str.size() == 2 && detail::equal2(format_str.data(), "{}")) {
+    auto arg = args.get(0);
+    if (!arg) detail::error_handler().on_error("argument not found");
+    using iterator = typename ArgFormatter::iterator;
+    return visit_format_arg(
+        detail::default_arg_formatter<iterator, Char>{out, args, loc}, arg);
+  }
+  detail::format_handler<ArgFormatter, Char, Context> h(out, format_str, args,
+                                                        loc);
+  detail::parse_format_string<false>(format_str, h);
+  return h.context.out();
+}
+
+// Casts ``p`` to ``const void*`` for pointer formatting.
+// Example:
+//   auto s = format("{}", ptr(p));
+template <typename T> inline const void* ptr(const T* p) { return p; }
+template <typename T> inline const void* ptr(const std::unique_ptr<T>& p) {
+  return p.get();
+}
+template <typename T> inline const void* ptr(const std::shared_ptr<T>& p) {
+  return p.get();
+}
+
+class bytes {
+ private:
+  string_view data_;
+  friend struct formatter<bytes>;
+
+ public:
+  explicit bytes(string_view data) : data_(data) {}
+};
+
+template <> struct formatter<bytes> {
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    using handler_type = detail::dynamic_specs_handler<ParseContext>;
+    detail::specs_checker<handler_type> handler(handler_type(specs_, ctx),
+                                                detail::type::string_type);
+    auto it = parse_format_specs(ctx.begin(), ctx.end(), handler);
+    detail::check_string_type_spec(specs_.type, ctx.error_handler());
+    return it;
+  }
+
+  template <typename FormatContext>
+  auto format(bytes b, FormatContext& ctx) -> decltype(ctx.out()) {
+    detail::handle_dynamic_spec<detail::width_checker>(specs_.width,
+                                                       specs_.width_ref, ctx);
+    detail::handle_dynamic_spec<detail::precision_checker>(
+        specs_.precision, specs_.precision_ref, ctx);
+    return detail::write_bytes(ctx.out(), b.data_, specs_);
+  }
+
+ private:
+  detail::dynamic_format_specs<char> specs_;
+};
+
+template <typename It, typename Sentinel, typename Char>
+struct arg_join : detail::view {
+  It begin;
+  Sentinel end;
+  basic_string_view<Char> sep;
+
+  arg_join(It b, Sentinel e, basic_string_view<Char> s)
+      : begin(b), end(e), sep(s) {}
+};
+
+template <typename It, typename Sentinel, typename Char>
+struct formatter<arg_join<It, Sentinel, Char>, Char>
+    : formatter<typename std::iterator_traits<It>::value_type, Char> {
+  template <typename FormatContext>
+  auto format(const arg_join<It, Sentinel, Char>& value, FormatContext& ctx)
+      -> decltype(ctx.out()) {
+    using base = formatter<typename std::iterator_traits<It>::value_type, Char>;
+    auto it = value.begin;
+    auto out = ctx.out();
+    if (it != value.end) {
+      out = base::format(*it++, ctx);
+      while (it != value.end) {
+        out = std::copy(value.sep.begin(), value.sep.end(), out);
+        ctx.advance_to(out);
+        out = base::format(*it++, ctx);
+      }
+    }
+    return out;
+  }
+};
+
+/**
+  Returns an object that formats the iterator range `[begin, end)` with elements
+  separated by `sep`.
+ */
+template <typename It, typename Sentinel>
+arg_join<It, Sentinel, char> join(It begin, Sentinel end, string_view sep) {
+  return {begin, end, sep};
+}
+
+template <typename It, typename Sentinel>
+arg_join<It, Sentinel, wchar_t> join(It begin, Sentinel end, wstring_view sep) {
+  return {begin, end, sep};
+}
+
+/**
+  \rst
+  Returns an object that formats `range` with elements separated by `sep`.
+
+  **Example**::
+
+    std::vector<int> v = {1, 2, 3};
+    fmt::print("{}", fmt::join(v, ", "));
+    // Output: "1, 2, 3"
+
+  ``fmt::join`` applies passed format specifiers to the range elements::
+
+    fmt::print("{:02}", fmt::join(v, ", "));
+    // Output: "01, 02, 03"
+  \endrst
+ */
+template <typename Range>
+arg_join<detail::iterator_t<const Range>, detail::sentinel_t<const Range>, char>
+join(const Range& range, string_view sep) {
+  return join(std::begin(range), std::end(range), sep);
+}
+
+template <typename Range>
+arg_join<detail::iterator_t<const Range>, detail::sentinel_t<const Range>,
+         wchar_t>
+join(const Range& range, wstring_view sep) {
+  return join(std::begin(range), std::end(range), sep);
+}
+
+/**
+  \rst
+  Converts *value* to ``std::string`` using the default format for type *T*.
+
+  **Example**::
+
+    #include <fmt/format.h>
+
+    std::string answer = fmt::to_string(42);
+  \endrst
+ */
+template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
+inline std::string to_string(const T& value) {
+  std::string result;
+  detail::write<char>(std::back_inserter(result), value);
+  return result;
+}
+
+template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
+inline std::string to_string(T value) {
+  // The buffer should be large enough to store the number including the sign or
+  // "false" for bool.
+  constexpr int max_size = detail::digits10<T>() + 2;
+  char buffer[max_size > 5 ? max_size : 5];
+  char* begin = buffer;
+  return std::string(begin, detail::write<char>(begin, value));
+}
+
+/**
+  Converts *value* to ``std::wstring`` using the default format for type *T*.
+ */
+template <typename T> inline std::wstring to_wstring(const T& value) {
+  return format(L"{}", value);
+}
+
+template <typename Char, size_t SIZE>
+std::basic_string<Char> to_string(const basic_memory_buffer<Char, SIZE>& buf) {
+  auto size = buf.size();
+  detail::assume(size < std::basic_string<Char>().max_size());
+  return std::basic_string<Char>(buf.data(), size);
+}
+
+template <typename Char>
+typename buffer_context<Char>::iterator detail::vformat_to(
+    detail::buffer<Char>& buf, basic_string_view<Char> format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+  using af = arg_formatter<typename buffer_context<Char>::iterator, Char>;
+  return vformat_to<af>(std::back_inserter(buf), to_string_view(format_str),
+                        args);
+}
+
+#ifndef FMT_HEADER_ONLY
+extern template format_context::iterator detail::vformat_to(
+    detail::buffer<char>&, string_view, basic_format_args<format_context>);
+namespace detail {
+extern template FMT_API std::string grouping_impl<char>(locale_ref loc);
+extern template FMT_API std::string grouping_impl<wchar_t>(locale_ref loc);
+extern template FMT_API char thousands_sep_impl<char>(locale_ref loc);
+extern template FMT_API wchar_t thousands_sep_impl<wchar_t>(locale_ref loc);
+extern template FMT_API char decimal_point_impl(locale_ref loc);
+extern template FMT_API wchar_t decimal_point_impl(locale_ref loc);
+extern template int format_float<double>(double value, int precision,
+                                         float_specs specs, buffer<char>& buf);
+extern template int format_float<long double>(long double value, int precision,
+                                              float_specs specs,
+                                              buffer<char>& buf);
+int snprintf_float(float value, int precision, float_specs specs,
+                   buffer<char>& buf) = delete;
+extern template int snprintf_float<double>(double value, int precision,
+                                           float_specs specs,
+                                           buffer<char>& buf);
+extern template int snprintf_float<long double>(long double value,
+                                                int precision,
+                                                float_specs specs,
+                                                buffer<char>& buf);
+}  // namespace detail
+#endif
+
+template <typename S, typename Char = char_t<S>,
+          FMT_ENABLE_IF(detail::is_string<S>::value)>
+inline typename FMT_BUFFER_CONTEXT(Char)::iterator vformat_to(
+    detail::buffer<Char>& buf, const S& format_str,
+    basic_format_args<FMT_BUFFER_CONTEXT(type_identity_t<Char>)> args) {
+  return detail::vformat_to(buf, to_string_view(format_str), args);
+}
+
+template <typename S, typename... Args, size_t SIZE = inline_buffer_size,
+          typename Char = enable_if_t<detail::is_string<S>::value, char_t<S>>>
+inline typename buffer_context<Char>::iterator format_to(
+    basic_memory_buffer<Char, SIZE>& buf, const S& format_str, Args&&... args) {
+  detail::check_format_string<Args...>(format_str);
+  using context = buffer_context<Char>;
+  return detail::vformat_to(buf, to_string_view(format_str),
+                            make_format_args<context>(args...));
+}
+
+template <typename OutputIt, typename Char = char>
+using format_context_t = basic_format_context<OutputIt, Char>;
+
+template <typename OutputIt, typename Char = char>
+using format_args_t = basic_format_args<format_context_t<OutputIt, Char>>;
+
+template <
+    typename S, typename OutputIt, typename... Args,
+    FMT_ENABLE_IF(detail::is_output_iterator<OutputIt>::value &&
+                  !detail::is_contiguous_back_insert_iterator<OutputIt>::value)>
+inline OutputIt vformat_to(
+    OutputIt out, const S& format_str,
+    format_args_t<type_identity_t<OutputIt>, char_t<S>> args) {
+  using af = detail::arg_formatter<OutputIt, char_t<S>>;
+  return vformat_to<af>(out, to_string_view(format_str), args);
+}
+
+/**
+ \rst
+ Formats arguments, writes the result to the output iterator ``out`` and returns
+ the iterator past the end of the output range.
+
+ **Example**::
+
+   std::vector<char> out;
+   fmt::format_to(std::back_inserter(out), "{}", 42);
+ \endrst
+ */
+template <typename OutputIt, typename S, typename... Args,
+          FMT_ENABLE_IF(
+              detail::is_output_iterator<OutputIt>::value &&
+              !detail::is_contiguous_back_insert_iterator<OutputIt>::value &&
+              detail::is_string<S>::value)>
+inline OutputIt format_to(OutputIt out, const S& format_str, Args&&... args) {
+  detail::check_format_string<Args...>(format_str);
+  using context = format_context_t<OutputIt, char_t<S>>;
+  return vformat_to(out, to_string_view(format_str),
+                    make_format_args<context>(args...));
+}
+
+template <typename OutputIt> struct format_to_n_result {
+  /** Iterator past the end of the output range. */
+  OutputIt out;
+  /** Total (not truncated) output size. */
+  size_t size;
+};
+
+template <typename OutputIt, typename Char = typename OutputIt::value_type>
+using format_to_n_context =
+    format_context_t<detail::truncating_iterator<OutputIt>, Char>;
+
+template <typename OutputIt, typename Char = typename OutputIt::value_type>
+using format_to_n_args = basic_format_args<format_to_n_context<OutputIt, Char>>;
+
+template <typename OutputIt, typename Char, typename... Args>
+inline format_arg_store<format_to_n_context<OutputIt, Char>, Args...>
+make_format_to_n_args(const Args&... args) {
+  return format_arg_store<format_to_n_context<OutputIt, Char>, Args...>(
+      args...);
+}
+
+template <typename OutputIt, typename Char, typename... Args,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt>::value)>
+inline format_to_n_result<OutputIt> vformat_to_n(
+    OutputIt out, size_t n, basic_string_view<Char> format_str,
+    format_to_n_args<type_identity_t<OutputIt>, type_identity_t<Char>> args) {
+  auto it = vformat_to(detail::truncating_iterator<OutputIt>(out, n),
+                       format_str, args);
+  return {it.base(), it.count()};
+}
+
+/**
+ \rst
+ Formats arguments, writes up to ``n`` characters of the result to the output
+ iterator ``out`` and returns the total output size and the iterator past the
+ end of the output range.
+ \endrst
+ */
+template <typename OutputIt, typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_string<S>::value&&
+                            detail::is_output_iterator<OutputIt>::value)>
+inline format_to_n_result<OutputIt> format_to_n(OutputIt out, size_t n,
+                                                const S& format_str,
+                                                const Args&... args) {
+  detail::check_format_string<Args...>(format_str);
+  using context = format_to_n_context<OutputIt, char_t<S>>;
+  return vformat_to_n(out, n, to_string_view(format_str),
+                      make_format_args<context>(args...));
+}
+
+template <typename Char, enable_if_t<(!std::is_same<Char, char>::value), int>>
+std::basic_string<Char> detail::vformat(
+    basic_string_view<Char> format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+  basic_memory_buffer<Char> buffer;
+  detail::vformat_to(buffer, format_str, args);
+  return to_string(buffer);
+}
+
+/**
+  Returns the number of characters in the output of
+  ``format(format_str, args...)``.
+ */
+template <typename... Args>
+inline size_t formatted_size(string_view format_str, const Args&... args) {
+  return format_to(detail::counting_iterator(), format_str, args...).count();
+}
+
+template <typename Char, FMT_ENABLE_IF(std::is_same<Char, wchar_t>::value)>
+void vprint(std::FILE* f, basic_string_view<Char> format_str,
+            wformat_args args) {
+  wmemory_buffer buffer;
+  detail::vformat_to(buffer, format_str, args);
+  buffer.push_back(L'\0');
+  if (std::fputws(buffer.data(), f) == -1)
+    FMT_THROW(system_error(errno, "cannot write to file"));
+}
+
+template <typename Char, FMT_ENABLE_IF(std::is_same<Char, wchar_t>::value)>
+void vprint(basic_string_view<Char> format_str, wformat_args args) {
+  vprint(stdout, format_str, args);
+}
+
+#if FMT_USE_USER_DEFINED_LITERALS
+namespace detail {
+
+#  if FMT_USE_UDL_TEMPLATE
+template <typename Char, Char... CHARS> class udl_formatter {
+ public:
+  template <typename... Args>
+  std::basic_string<Char> operator()(Args&&... args) const {
+    static FMT_CONSTEXPR_DECL Char s[] = {CHARS..., '\0'};
+    check_format_string<remove_cvref_t<Args>...>(FMT_STRING(s));
+    return format(s, std::forward<Args>(args)...);
+  }
+};
+#  else
+template <typename Char> struct udl_formatter {
+  basic_string_view<Char> str;
+
+  template <typename... Args>
+  std::basic_string<Char> operator()(Args&&... args) const {
+    return format(str, std::forward<Args>(args)...);
+  }
+};
+#  endif  // FMT_USE_UDL_TEMPLATE
+
+template <typename Char> struct udl_arg {
+  const Char* str;
+
+  template <typename T> named_arg<Char, T> operator=(T&& value) const {
+    return {str, std::forward<T>(value)};
+  }
+};
+}  // namespace detail
+
+inline namespace literals {
+#  if FMT_USE_UDL_TEMPLATE
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wpedantic"
+#    if FMT_CLANG_VERSION
+#      pragma GCC diagnostic ignored "-Wgnu-string-literal-operator-template"
+#    endif
+template <typename Char, Char... CHARS>
+FMT_CONSTEXPR detail::udl_formatter<Char, CHARS...> operator""_format() {
+  return {};
+}
+#    pragma GCC diagnostic pop
+#  else
+/**
+  \rst
+  User-defined literal equivalent of :func:`fmt::format`.
+
+  **Example**::
+
+    using namespace fmt::literals;
+    std::string message = "The answer is {}"_format(42);
+  \endrst
+ */
+FMT_CONSTEXPR detail::udl_formatter<char> operator"" _format(const char* s,
+                                                             size_t n) {
+  return {{s, n}};
+}
+FMT_CONSTEXPR detail::udl_formatter<wchar_t> operator"" _format(
+    const wchar_t* s, size_t n) {
+  return {{s, n}};
+}
+#  endif  // FMT_USE_UDL_TEMPLATE
+
+/**
+  \rst
+  User-defined literal equivalent of :func:`fmt::arg`.
+
+  **Example**::
+
+    using namespace fmt::literals;
+    fmt::print("Elapsed time: {s:.2f} seconds", "s"_a=1.23);
+  \endrst
+ */
+FMT_CONSTEXPR detail::udl_arg<char> operator"" _a(const char* s, size_t) {
+  return {s};
+}
+FMT_CONSTEXPR detail::udl_arg<wchar_t> operator"" _a(const wchar_t* s, size_t) {
+  return {s};
+}
+}  // namespace literals
+#endif  // FMT_USE_USER_DEFINED_LITERALS
+FMT_END_NAMESPACE
+
+#ifdef FMT_HEADER_ONLY
+#  define FMT_FUNC inline
+#  include "format-inl.h"
+#else
+#  define FMT_FUNC
+#endif
+
+#endif  // FMT_FORMAT_H_
diff --git a/external/fmtlib/include/fmt/locale.h b/external/fmtlib/include/fmt/locale.h
new file mode 100644
index 000000000..988d15cdf
--- /dev/null
+++ b/external/fmtlib/include/fmt/locale.h
@@ -0,0 +1,78 @@
+// Formatting library for C++ - std::locale support
+//
+// Copyright (c) 2012 - present, Victor Zverovich
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+#ifndef FMT_LOCALE_H_
+#define FMT_LOCALE_H_
+
+#include <locale>
+
+#include "format.h"
+
+FMT_BEGIN_NAMESPACE
+
+namespace detail {
+template <typename Char>
+typename buffer_context<Char>::iterator vformat_to(
+    const std::locale& loc, buffer<Char>& buf,
+    basic_string_view<Char> format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+  using af = arg_formatter<typename buffer_context<Char>::iterator, Char>;
+  return vformat_to<af>(std::back_inserter(buf), to_string_view(format_str),
+                        args, detail::locale_ref(loc));
+}
+
+template <typename Char>
+std::basic_string<Char> vformat(
+    const std::locale& loc, basic_string_view<Char> format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+  basic_memory_buffer<Char> buffer;
+  detail::vformat_to(loc, buffer, format_str, args);
+  return fmt::to_string(buffer);
+}
+}  // namespace detail
+
+template <typename S, typename Char = char_t<S>>
+inline std::basic_string<Char> vformat(
+    const std::locale& loc, const S& format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+  return detail::vformat(loc, to_string_view(format_str), args);
+}
+
+template <typename S, typename... Args, typename Char = char_t<S>>
+inline std::basic_string<Char> format(const std::locale& loc,
+                                      const S& format_str, Args&&... args) {
+  return detail::vformat(
+      loc, to_string_view(format_str),
+      detail::make_args_checked<Args...>(format_str, args...));
+}
+
+template <typename S, typename OutputIt, typename... Args,
+          typename Char = enable_if_t<
+              detail::is_output_iterator<OutputIt>::value, char_t<S>>>
+inline OutputIt vformat_to(
+    OutputIt out, const std::locale& loc, const S& format_str,
+    format_args_t<type_identity_t<OutputIt>, Char> args) {
+  using af = detail::arg_formatter<OutputIt, Char>;
+  return vformat_to<af>(out, to_string_view(format_str), args,
+                        detail::locale_ref(loc));
+}
+
+template <typename OutputIt, typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt>::value&&
+                            detail::is_string<S>::value)>
+inline OutputIt format_to(OutputIt out, const std::locale& loc,
+                          const S& format_str, Args&&... args) {
+  detail::check_format_string<Args...>(format_str);
+  using context = format_context_t<OutputIt, char_t<S>>;
+  format_arg_store<context, Args...> as{args...};
+  return vformat_to(out, loc, to_string_view(format_str),
+                    basic_format_args<context>(as));
+}
+
+FMT_END_NAMESPACE
+
+#endif  // FMT_LOCALE_H_
diff --git a/external/fmtlib/include/fmt/os.h b/external/fmtlib/include/fmt/os.h
new file mode 100644
index 000000000..a9517ef80
--- /dev/null
+++ b/external/fmtlib/include/fmt/os.h
@@ -0,0 +1,450 @@
+// Formatting library for C++ - optional OS-specific functionality
+//
+// Copyright (c) 2012 - present, Victor Zverovich
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+#ifndef FMT_OS_H_
+#define FMT_OS_H_
+
+#if defined(__MINGW32__) || defined(__CYGWIN__)
+// Workaround MinGW bug https://sourceforge.net/p/mingw/bugs/2024/.
+#  undef __STRICT_ANSI__
+#endif
+
+#include <cerrno>
+#include <clocale>  // for locale_t
+#include <cstddef>
+#include <cstdio>
+#include <cstdlib>  // for strtod_l
+
+#if defined __APPLE__ || defined(__FreeBSD__)
+#  include <xlocale.h>  // for LC_NUMERIC_MASK on OS X
+#endif
+
+#include "format.h"
+
+// UWP doesn't provide _pipe.
+#if FMT_HAS_INCLUDE("winapifamily.h")
+#  include <winapifamily.h>
+#endif
+#if FMT_HAS_INCLUDE("fcntl.h") && \
+    (!defined(WINAPI_FAMILY) || (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP))
+#  include <fcntl.h>  // for O_RDONLY
+#  define FMT_USE_FCNTL 1
+#else
+#  define FMT_USE_FCNTL 0
+#endif
+
+#ifndef FMT_POSIX
+#  if defined(_WIN32) && !defined(__MINGW32__)
+// Fix warnings about deprecated symbols.
+#    define FMT_POSIX(call) _##call
+#  else
+#    define FMT_POSIX(call) call
+#  endif
+#endif
+
+// Calls to system functions are wrapped in FMT_SYSTEM for testability.
+#ifdef FMT_SYSTEM
+#  define FMT_POSIX_CALL(call) FMT_SYSTEM(call)
+#else
+#  define FMT_SYSTEM(call) ::call
+#  ifdef _WIN32
+// Fix warnings about deprecated symbols.
+#    define FMT_POSIX_CALL(call) ::_##call
+#  else
+#    define FMT_POSIX_CALL(call) ::call
+#  endif
+#endif
+
+// Retries the expression while it evaluates to error_result and errno
+// equals to EINTR.
+#ifndef _WIN32
+#  define FMT_RETRY_VAL(result, expression, error_result) \
+    do {                                                  \
+      (result) = (expression);                            \
+    } while ((result) == (error_result) && errno == EINTR)
+#else
+#  define FMT_RETRY_VAL(result, expression, error_result) result = (expression)
+#endif
+
+#define FMT_RETRY(result, expression) FMT_RETRY_VAL(result, expression, -1)
+
+FMT_BEGIN_NAMESPACE
+
+/**
+  \rst
+  A reference to a null-terminated string. It can be constructed from a C
+  string or ``std::string``.
+
+  You can use one of the following type aliases for common character types:
+
+  +---------------+-----------------------------+
+  | Type          | Definition                  |
+  +===============+=============================+
+  | cstring_view  | basic_cstring_view<char>    |
+  +---------------+-----------------------------+
+  | wcstring_view | basic_cstring_view<wchar_t> |
+  +---------------+-----------------------------+
+
+  This class is most useful as a parameter type to allow passing
+  different types of strings to a function, for example::
+
+    template <typename... Args>
+    std::string format(cstring_view format_str, const Args & ... args);
+
+    format("{}", 42);
+    format(std::string("{}"), 42);
+  \endrst
+ */
+template <typename Char> class basic_cstring_view {
+ private:
+  const Char* data_;
+
+ public:
+  /** Constructs a string reference object from a C string. */
+  basic_cstring_view(const Char* s) : data_(s) {}
+
+  /**
+    \rst
+    Constructs a string reference from an ``std::string`` object.
+    \endrst
+   */
+  basic_cstring_view(const std::basic_string<Char>& s) : data_(s.c_str()) {}
+
+  /** Returns the pointer to a C string. */
+  const Char* c_str() const { return data_; }
+};
+
+using cstring_view = basic_cstring_view<char>;
+using wcstring_view = basic_cstring_view<wchar_t>;
+
+// An error code.
+class error_code {
+ private:
+  int value_;
+
+ public:
+  explicit error_code(int value = 0) FMT_NOEXCEPT : value_(value) {}
+
+  int get() const FMT_NOEXCEPT { return value_; }
+};
+
+#ifdef _WIN32
+namespace detail {
+// A converter from UTF-16 to UTF-8.
+// It is only provided for Windows since other systems support UTF-8 natively.
+class utf16_to_utf8 {
+ private:
+  memory_buffer buffer_;
+
+ public:
+  utf16_to_utf8() {}
+  FMT_API explicit utf16_to_utf8(wstring_view s);
+  operator string_view() const { return string_view(&buffer_[0], size()); }
+  size_t size() const { return buffer_.size() - 1; }
+  const char* c_str() const { return &buffer_[0]; }
+  std::string str() const { return std::string(&buffer_[0], size()); }
+
+  // Performs conversion returning a system error code instead of
+  // throwing exception on conversion error. This method may still throw
+  // in case of memory allocation error.
+  FMT_API int convert(wstring_view s);
+};
+
+FMT_API void format_windows_error(buffer<char>& out, int error_code,
+                                  string_view message) FMT_NOEXCEPT;
+}  // namespace detail
+
+/** A Windows error. */
+class windows_error : public system_error {
+ private:
+  FMT_API void init(int error_code, string_view format_str, format_args args);
+
+ public:
+  /**
+   \rst
+   Constructs a :class:`fmt::windows_error` object with the description
+   of the form
+
+   .. parsed-literal::
+     *<message>*: *<system-message>*
+
+   where *<message>* is the formatted message and *<system-message>* is the
+   system message corresponding to the error code.
+   *error_code* is a Windows error code as given by ``GetLastError``.
+   If *error_code* is not a valid error code such as -1, the system message
+   will look like "error -1".
+
+   **Example**::
+
+     // This throws a windows_error with the description
+     //   cannot open file 'madeup': The system cannot find the file specified.
+     // or similar (system message may vary).
+     const char *filename = "madeup";
+     LPOFSTRUCT of = LPOFSTRUCT();
+     HFILE file = OpenFile(filename, &of, OF_READ);
+     if (file == HFILE_ERROR) {
+       throw fmt::windows_error(GetLastError(),
+                                "cannot open file '{}'", filename);
+     }
+   \endrst
+  */
+  template <typename... Args>
+  windows_error(int error_code, string_view message, const Args&... args) {
+    init(error_code, message, make_format_args(args...));
+  }
+};
+
+// Reports a Windows error without throwing an exception.
+// Can be used to report errors from destructors.
+FMT_API void report_windows_error(int error_code,
+                                  string_view message) FMT_NOEXCEPT;
+#endif  // _WIN32
+
+// A buffered file.
+class buffered_file {
+ private:
+  FILE* file_;
+
+  friend class file;
+
+  explicit buffered_file(FILE* f) : file_(f) {}
+
+ public:
+  buffered_file(const buffered_file&) = delete;
+  void operator=(const buffered_file&) = delete;
+
+  // Constructs a buffered_file object which doesn't represent any file.
+  buffered_file() FMT_NOEXCEPT : file_(nullptr) {}
+
+  // Destroys the object closing the file it represents if any.
+  FMT_API ~buffered_file() FMT_NOEXCEPT;
+
+ public:
+  buffered_file(buffered_file&& other) FMT_NOEXCEPT : file_(other.file_) {
+    other.file_ = nullptr;
+  }
+
+  buffered_file& operator=(buffered_file&& other) {
+    close();
+    file_ = other.file_;
+    other.file_ = nullptr;
+    return *this;
+  }
+
+  // Opens a file.
+  FMT_API buffered_file(cstring_view filename, cstring_view mode);
+
+  // Closes the file.
+  FMT_API void close();
+
+  // Returns the pointer to a FILE object representing this file.
+  FILE* get() const FMT_NOEXCEPT { return file_; }
+
+  // We place parentheses around fileno to workaround a bug in some versions
+  // of MinGW that define fileno as a macro.
+  FMT_API int(fileno)() const;
+
+  void vprint(string_view format_str, format_args args) {
+    fmt::vprint(file_, format_str, args);
+  }
+
+  template <typename... Args>
+  inline void print(string_view format_str, const Args&... args) {
+    vprint(format_str, make_format_args(args...));
+  }
+};
+
+#if FMT_USE_FCNTL
+// A file. Closed file is represented by a file object with descriptor -1.
+// Methods that are not declared with FMT_NOEXCEPT may throw
+// fmt::system_error in case of failure. Note that some errors such as
+// closing the file multiple times will cause a crash on Windows rather
+// than an exception. You can get standard behavior by overriding the
+// invalid parameter handler with _set_invalid_parameter_handler.
+class file {
+ private:
+  int fd_;  // File descriptor.
+
+  // Constructs a file object with a given descriptor.
+  explicit file(int fd) : fd_(fd) {}
+
+ public:
+  // Possible values for the oflag argument to the constructor.
+  enum {
+    RDONLY = FMT_POSIX(O_RDONLY),  // Open for reading only.
+    WRONLY = FMT_POSIX(O_WRONLY),  // Open for writing only.
+    RDWR = FMT_POSIX(O_RDWR),      // Open for reading and writing.
+    CREATE = FMT_POSIX(O_CREAT)    // Create if the file doesn't exist.
+  };
+
+  // Constructs a file object which doesn't represent any file.
+  file() FMT_NOEXCEPT : fd_(-1) {}
+
+  // Opens a file and constructs a file object representing this file.
+  FMT_API file(cstring_view path, int oflag);
+
+ public:
+  file(const file&) = delete;
+  void operator=(const file&) = delete;
+
+  file(file&& other) FMT_NOEXCEPT : fd_(other.fd_) { other.fd_ = -1; }
+
+  file& operator=(file&& other) FMT_NOEXCEPT {
+    close();
+    fd_ = other.fd_;
+    other.fd_ = -1;
+    return *this;
+  }
+
+  // Destroys the object closing the file it represents if any.
+  FMT_API ~file() FMT_NOEXCEPT;
+
+  // Returns the file descriptor.
+  int descriptor() const FMT_NOEXCEPT { return fd_; }
+
+  // Closes the file.
+  FMT_API void close();
+
+  // Returns the file size. The size has signed type for consistency with
+  // stat::st_size.
+  FMT_API long long size() const;
+
+  // Attempts to read count bytes from the file into the specified buffer.
+  FMT_API size_t read(void* buffer, size_t count);
+
+  // Attempts to write count bytes from the specified buffer to the file.
+  FMT_API size_t write(const void* buffer, size_t count);
+
+  // Duplicates a file descriptor with the dup function and returns
+  // the duplicate as a file object.
+  FMT_API static file dup(int fd);
+
+  // Makes fd be the copy of this file descriptor, closing fd first if
+  // necessary.
+  FMT_API void dup2(int fd);
+
+  // Makes fd be the copy of this file descriptor, closing fd first if
+  // necessary.
+  FMT_API void dup2(int fd, error_code& ec) FMT_NOEXCEPT;
+
+  // Creates a pipe setting up read_end and write_end file objects for reading
+  // and writing respectively.
+  FMT_API static void pipe(file& read_end, file& write_end);
+
+  // Creates a buffered_file object associated with this file and detaches
+  // this file object from the file.
+  FMT_API buffered_file fdopen(const char* mode);
+};
+
+// Returns the memory page size.
+long getpagesize();
+
+class direct_buffered_file;
+
+template <typename S, typename... Args>
+void print(direct_buffered_file& f, const S& format_str,
+           const Args&... args);
+
+// A buffered file with a direct buffer access and no synchronization.
+class direct_buffered_file {
+ private:
+  file file_;
+
+  enum { buffer_size = 4096 };
+  char buffer_[buffer_size];
+  int pos_;
+
+  void flush() {
+    if (pos_ == 0) return;
+    file_.write(buffer_, pos_);
+    pos_ = 0;
+  }
+
+  int free_capacity() const { return buffer_size - pos_; }
+
+ public:
+  direct_buffered_file(cstring_view path, int oflag)
+    : file_(path, oflag), pos_(0) {}
+
+  ~direct_buffered_file() {
+    flush();
+  }
+
+  void close() {
+    flush();
+    file_.close();
+  }
+
+  template <typename S, typename... Args>
+  friend void print(direct_buffered_file& f, const S& format_str,
+                    const Args&... args) {
+    // We could avoid double buffering.
+    auto buf = fmt::memory_buffer();
+    fmt::format_to(std::back_inserter(buf), format_str, args...);
+    auto remaining_pos = 0;
+    auto remaining_size = buf.size();
+    while (remaining_size > detail::to_unsigned(f.free_capacity())) {
+      auto size = f.free_capacity();
+      memcpy(f.buffer_ + f.pos_, buf.data() + remaining_pos, size);
+      f.pos_ += size;
+      f.flush();
+      remaining_pos += size;
+      remaining_size -= size;
+    }
+    memcpy(f.buffer_ + f.pos_, buf.data() + remaining_pos, remaining_size);
+    f.pos_ += static_cast<int>(remaining_size);
+  }
+};
+#endif  // FMT_USE_FCNTL
+
+#ifdef FMT_LOCALE
+// A "C" numeric locale.
+class locale {
+ private:
+#  ifdef _WIN32
+  using locale_t = _locale_t;
+
+  static void freelocale(locale_t loc) { _free_locale(loc); }
+
+  static double strtod_l(const char* nptr, char** endptr, _locale_t loc) {
+    return _strtod_l(nptr, endptr, loc);
+  }
+#  endif
+
+  locale_t locale_;
+
+ public:
+  using type = locale_t;
+  locale(const locale&) = delete;
+  void operator=(const locale&) = delete;
+
+  locale() {
+#  ifndef _WIN32
+    locale_ = FMT_SYSTEM(newlocale(LC_NUMERIC_MASK, "C", nullptr));
+#  else
+    locale_ = _create_locale(LC_NUMERIC, "C");
+#  endif
+    if (!locale_) FMT_THROW(system_error(errno, "cannot create locale"));
+  }
+  ~locale() { freelocale(locale_); }
+
+  type get() const { return locale_; }
+
+  // Converts string to floating-point number and advances str past the end
+  // of the parsed input.
+  double strtod(const char*& str) const {
+    char* end = nullptr;
+    double result = strtod_l(str, &end, locale_);
+    str = end;
+    return result;
+  }
+};
+using Locale FMT_DEPRECATED_ALIAS = locale;
+#endif  // FMT_LOCALE
+FMT_END_NAMESPACE
+
+#endif  // FMT_OS_H_
diff --git a/external/fmtlib/include/fmt/ostream.h b/external/fmtlib/include/fmt/ostream.h
new file mode 100644
index 000000000..c16107f79
--- /dev/null
+++ b/external/fmtlib/include/fmt/ostream.h
@@ -0,0 +1,167 @@
+// Formatting library for C++ - std::ostream support
+//
+// Copyright (c) 2012 - present, Victor Zverovich
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+#ifndef FMT_OSTREAM_H_
+#define FMT_OSTREAM_H_
+
+#include <ostream>
+
+#include "format.h"
+
+FMT_BEGIN_NAMESPACE
+
+template <typename Char> class basic_printf_parse_context;
+template <typename OutputIt, typename Char> class basic_printf_context;
+
+namespace detail {
+
+template <class Char> class formatbuf : public std::basic_streambuf<Char> {
+ private:
+  using int_type = typename std::basic_streambuf<Char>::int_type;
+  using traits_type = typename std::basic_streambuf<Char>::traits_type;
+
+  buffer<Char>& buffer_;
+
+ public:
+  formatbuf(buffer<Char>& buf) : buffer_(buf) {}
+
+ protected:
+  // The put-area is actually always empty. This makes the implementation
+  // simpler and has the advantage that the streambuf and the buffer are always
+  // in sync and sputc never writes into uninitialized memory. The obvious
+  // disadvantage is that each call to sputc always results in a (virtual) call
+  // to overflow. There is no disadvantage here for sputn since this always
+  // results in a call to xsputn.
+
+  int_type overflow(int_type ch = traits_type::eof()) FMT_OVERRIDE {
+    if (!traits_type::eq_int_type(ch, traits_type::eof()))
+      buffer_.push_back(static_cast<Char>(ch));
+    return ch;
+  }
+
+  std::streamsize xsputn(const Char* s, std::streamsize count) FMT_OVERRIDE {
+    buffer_.append(s, s + count);
+    return count;
+  }
+};
+
+template <typename Char> struct test_stream : std::basic_ostream<Char> {
+ private:
+  // Hide all operator<< from std::basic_ostream<Char>.
+  void_t<> operator<<(null<>);
+  void_t<> operator<<(const Char*);
+
+  template <typename T, FMT_ENABLE_IF(std::is_convertible<T, int>::value &&
+                                      !std::is_enum<T>::value)>
+  void_t<> operator<<(T);
+};
+
+// Checks if T has a user-defined operator<< (e.g. not a member of
+// std::ostream).
+template <typename T, typename Char> class is_streamable {
+ private:
+  template <typename U>
+  static bool_constant<!std::is_same<decltype(std::declval<test_stream<Char>&>()
+                                              << std::declval<U>()),
+                                     void_t<>>::value>
+  test(int);
+
+  template <typename> static std::false_type test(...);
+
+  using result = decltype(test<T>(0));
+
+ public:
+  static const bool value = result::value;
+};
+
+// Write the content of buf to os.
+template <typename Char>
+void write_buffer(std::basic_ostream<Char>& os, buffer<Char>& buf) {
+  const Char* buf_data = buf.data();
+  using unsigned_streamsize = std::make_unsigned<std::streamsize>::type;
+  unsigned_streamsize size = buf.size();
+  unsigned_streamsize max_size = to_unsigned(max_value<std::streamsize>());
+  do {
+    unsigned_streamsize n = size <= max_size ? size : max_size;
+    os.write(buf_data, static_cast<std::streamsize>(n));
+    buf_data += n;
+    size -= n;
+  } while (size != 0);
+}
+
+template <typename Char, typename T>
+void format_value(buffer<Char>& buf, const T& value,
+                  locale_ref loc = locale_ref()) {
+  formatbuf<Char> format_buf(buf);
+  std::basic_ostream<Char> output(&format_buf);
+#if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
+  if (loc) output.imbue(loc.get<std::locale>());
+#endif
+  output << value;
+  output.exceptions(std::ios_base::failbit | std::ios_base::badbit);
+  buf.resize(buf.size());
+}
+
+// Formats an object of type T that has an overloaded ostream operator<<.
+template <typename T, typename Char>
+struct fallback_formatter<T, Char, enable_if_t<is_streamable<T, Char>::value>>
+    : private formatter<basic_string_view<Char>, Char> {
+  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
+      -> decltype(ctx.begin()) {
+    return formatter<basic_string_view<Char>, Char>::parse(ctx);
+  }
+  template <typename ParseCtx,
+            FMT_ENABLE_IF(std::is_same<
+                          ParseCtx, basic_printf_parse_context<Char>>::value)>
+  auto parse(ParseCtx& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename OutputIt>
+  auto format(const T& value, basic_format_context<OutputIt, Char>& ctx)
+      -> OutputIt {
+    basic_memory_buffer<Char> buffer;
+    format_value(buffer, value, ctx.locale());
+    basic_string_view<Char> str(buffer.data(), buffer.size());
+    return formatter<basic_string_view<Char>, Char>::format(str, ctx);
+  }
+  template <typename OutputIt>
+  auto format(const T& value, basic_printf_context<OutputIt, Char>& ctx)
+      -> OutputIt {
+    basic_memory_buffer<Char> buffer;
+    format_value(buffer, value, ctx.locale());
+    return std::copy(buffer.begin(), buffer.end(), ctx.out());
+  }
+};
+}  // namespace detail
+
+template <typename Char>
+void vprint(std::basic_ostream<Char>& os, basic_string_view<Char> format_str,
+            basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+  basic_memory_buffer<Char> buffer;
+  detail::vformat_to(buffer, format_str, args);
+  detail::write_buffer(os, buffer);
+}
+
+/**
+  \rst
+  Prints formatted data to the stream *os*.
+
+  **Example**::
+
+    fmt::print(cerr, "Don't {}!", "panic");
+  \endrst
+ */
+template <typename S, typename... Args,
+          typename Char = enable_if_t<detail::is_string<S>::value, char_t<S>>>
+void print(std::basic_ostream<Char>& os, const S& format_str, Args&&... args) {
+  vprint(os, to_string_view(format_str),
+         detail::make_args_checked<Args...>(format_str, args...));
+}
+FMT_END_NAMESPACE
+
+#endif  // FMT_OSTREAM_H_
diff --git a/external/fmtlib/include/fmt/posix.h b/external/fmtlib/include/fmt/posix.h
new file mode 100644
index 000000000..da19e9d53
--- /dev/null
+++ b/external/fmtlib/include/fmt/posix.h
@@ -0,0 +1,2 @@
+#include "os.h"
+#warning "fmt/posix.h is deprecated; use fmt/os.h instead"
diff --git a/external/fmtlib/include/fmt/printf.h b/external/fmtlib/include/fmt/printf.h
new file mode 100644
index 000000000..d4440ed16
--- /dev/null
+++ b/external/fmtlib/include/fmt/printf.h
@@ -0,0 +1,751 @@
+// Formatting library for C++ - legacy printf implementation
+//
+// Copyright (c) 2012 - 2016, Victor Zverovich
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+#ifndef FMT_PRINTF_H_
+#define FMT_PRINTF_H_
+
+#include <algorithm>  // std::max
+#include <limits>     // std::numeric_limits
+
+#include "ostream.h"
+
+FMT_BEGIN_NAMESPACE
+namespace detail {
+
+// Checks if a value fits in int - used to avoid warnings about comparing
+// signed and unsigned integers.
+template <bool IsSigned> struct int_checker {
+  template <typename T> static bool fits_in_int(T value) {
+    unsigned max = max_value<int>();
+    return value <= max;
+  }
+  static bool fits_in_int(bool) { return true; }
+};
+
+template <> struct int_checker<true> {
+  template <typename T> static bool fits_in_int(T value) {
+    return value >= (std::numeric_limits<int>::min)() &&
+           value <= max_value<int>();
+  }
+  static bool fits_in_int(int) { return true; }
+};
+
+class printf_precision_handler {
+ public:
+  template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
+  int operator()(T value) {
+    if (!int_checker<std::numeric_limits<T>::is_signed>::fits_in_int(value))
+      FMT_THROW(format_error("number is too big"));
+    return (std::max)(static_cast<int>(value), 0);
+  }
+
+  template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
+  int operator()(T) {
+    FMT_THROW(format_error("precision is not integer"));
+    return 0;
+  }
+};
+
+// An argument visitor that returns true iff arg is a zero integer.
+class is_zero_int {
+ public:
+  template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
+  bool operator()(T value) {
+    return value == 0;
+  }
+
+  template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
+  bool operator()(T) {
+    return false;
+  }
+};
+
+template <typename T> struct make_unsigned_or_bool : std::make_unsigned<T> {};
+
+template <> struct make_unsigned_or_bool<bool> { using type = bool; };
+
+template <typename T, typename Context> class arg_converter {
+ private:
+  using char_type = typename Context::char_type;
+
+  basic_format_arg<Context>& arg_;
+  char_type type_;
+
+ public:
+  arg_converter(basic_format_arg<Context>& arg, char_type type)
+      : arg_(arg), type_(type) {}
+
+  void operator()(bool value) {
+    if (type_ != 's') operator()<bool>(value);
+  }
+
+  template <typename U, FMT_ENABLE_IF(std::is_integral<U>::value)>
+  void operator()(U value) {
+    bool is_signed = type_ == 'd' || type_ == 'i';
+    using target_type = conditional_t<std::is_same<T, void>::value, U, T>;
+    if (const_check(sizeof(target_type) <= sizeof(int))) {
+      // Extra casts are used to silence warnings.
+      if (is_signed) {
+        arg_ = detail::make_arg<Context>(
+            static_cast<int>(static_cast<target_type>(value)));
+      } else {
+        using unsigned_type = typename make_unsigned_or_bool<target_type>::type;
+        arg_ = detail::make_arg<Context>(
+            static_cast<unsigned>(static_cast<unsigned_type>(value)));
+      }
+    } else {
+      if (is_signed) {
+        // glibc's printf doesn't sign extend arguments of smaller types:
+        //   std::printf("%lld", -42);  // prints "4294967254"
+        // but we don't have to do the same because it's a UB.
+        arg_ = detail::make_arg<Context>(static_cast<long long>(value));
+      } else {
+        arg_ = detail::make_arg<Context>(
+            static_cast<typename make_unsigned_or_bool<U>::type>(value));
+      }
+    }
+  }
+
+  template <typename U, FMT_ENABLE_IF(!std::is_integral<U>::value)>
+  void operator()(U) {}  // No conversion needed for non-integral types.
+};
+
+// Converts an integer argument to T for printf, if T is an integral type.
+// If T is void, the argument is converted to corresponding signed or unsigned
+// type depending on the type specifier: 'd' and 'i' - signed, other -
+// unsigned).
+template <typename T, typename Context, typename Char>
+void convert_arg(basic_format_arg<Context>& arg, Char type) {
+  visit_format_arg(arg_converter<T, Context>(arg, type), arg);
+}
+
+// Converts an integer argument to char for printf.
+template <typename Context> class char_converter {
+ private:
+  basic_format_arg<Context>& arg_;
+
+ public:
+  explicit char_converter(basic_format_arg<Context>& arg) : arg_(arg) {}
+
+  template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
+  void operator()(T value) {
+    arg_ = detail::make_arg<Context>(
+        static_cast<typename Context::char_type>(value));
+  }
+
+  template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
+  void operator()(T) {}  // No conversion needed for non-integral types.
+};
+
+// An argument visitor that return a pointer to a C string if argument is a
+// string or null otherwise.
+template <typename Char> struct get_cstring {
+  template <typename T> const Char* operator()(T) { return nullptr; }
+  const Char* operator()(const Char* s) { return s; }
+};
+
+// Checks if an argument is a valid printf width specifier and sets
+// left alignment if it is negative.
+template <typename Char> class printf_width_handler {
+ private:
+  using format_specs = basic_format_specs<Char>;
+
+  format_specs& specs_;
+
+ public:
+  explicit printf_width_handler(format_specs& specs) : specs_(specs) {}
+
+  template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
+  unsigned operator()(T value) {
+    auto width = static_cast<uint32_or_64_or_128_t<T>>(value);
+    if (detail::is_negative(value)) {
+      specs_.align = align::left;
+      width = 0 - width;
+    }
+    unsigned int_max = max_value<int>();
+    if (width > int_max) FMT_THROW(format_error("number is too big"));
+    return static_cast<unsigned>(width);
+  }
+
+  template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
+  unsigned operator()(T) {
+    FMT_THROW(format_error("width is not integer"));
+    return 0;
+  }
+};
+
+template <typename Char, typename Context>
+void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
+             basic_format_args<Context> args) {
+  Context(std::back_inserter(buf), format, args).format();
+}
+}  // namespace detail
+
+// For printing into memory_buffer.
+template <typename Char, typename Context>
+FMT_DEPRECATED void printf(detail::buffer<Char>& buf,
+                           basic_string_view<Char> format,
+                           basic_format_args<Context> args) {
+  return detail::vprintf(buf, format, args);
+}
+using detail::vprintf;
+
+template <typename Char>
+class basic_printf_parse_context : public basic_format_parse_context<Char> {
+  using basic_format_parse_context<Char>::basic_format_parse_context;
+};
+template <typename OutputIt, typename Char> class basic_printf_context;
+
+/**
+  \rst
+  The ``printf`` argument formatter.
+  \endrst
+ */
+template <typename OutputIt, typename Char>
+class printf_arg_formatter : public detail::arg_formatter_base<OutputIt, Char> {
+ public:
+  using iterator = OutputIt;
+
+ private:
+  using char_type = Char;
+  using base = detail::arg_formatter_base<OutputIt, Char>;
+  using context_type = basic_printf_context<OutputIt, Char>;
+
+  context_type& context_;
+
+  void write_null_pointer(char) {
+    this->specs()->type = 0;
+    this->write("(nil)");
+  }
+
+  void write_null_pointer(wchar_t) {
+    this->specs()->type = 0;
+    this->write(L"(nil)");
+  }
+
+ public:
+  using format_specs = typename base::format_specs;
+
+  /**
+    \rst
+    Constructs an argument formatter object.
+    *buffer* is a reference to the output buffer and *specs* contains format
+    specifier information for standard argument types.
+    \endrst
+   */
+  printf_arg_formatter(iterator iter, format_specs& specs, context_type& ctx)
+      : base(iter, &specs, detail::locale_ref()), context_(ctx) {}
+
+  template <typename T, FMT_ENABLE_IF(fmt::detail::is_integral<T>::value)>
+  iterator operator()(T value) {
+    // MSVC2013 fails to compile separate overloads for bool and char_type so
+    // use std::is_same instead.
+    if (std::is_same<T, bool>::value) {
+      format_specs& fmt_specs = *this->specs();
+      if (fmt_specs.type != 's') return base::operator()(value ? 1 : 0);
+      fmt_specs.type = 0;
+      this->write(value != 0);
+    } else if (std::is_same<T, char_type>::value) {
+      format_specs& fmt_specs = *this->specs();
+      if (fmt_specs.type && fmt_specs.type != 'c')
+        return (*this)(static_cast<int>(value));
+      fmt_specs.sign = sign::none;
+      fmt_specs.alt = false;
+      fmt_specs.fill[0] = ' ';  // Ignore '0' flag for char types.
+      // align::numeric needs to be overwritten here since the '0' flag is
+      // ignored for non-numeric types
+      if (fmt_specs.align == align::none || fmt_specs.align == align::numeric)
+        fmt_specs.align = align::right;
+      return base::operator()(value);
+    } else {
+      return base::operator()(value);
+    }
+    return this->out();
+  }
+
+  template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
+  iterator operator()(T value) {
+    return base::operator()(value);
+  }
+
+  /** Formats a null-terminated C string. */
+  iterator operator()(const char* value) {
+    if (value)
+      base::operator()(value);
+    else if (this->specs()->type == 'p')
+      write_null_pointer(char_type());
+    else
+      this->write("(null)");
+    return this->out();
+  }
+
+  /** Formats a null-terminated wide C string. */
+  iterator operator()(const wchar_t* value) {
+    if (value)
+      base::operator()(value);
+    else if (this->specs()->type == 'p')
+      write_null_pointer(char_type());
+    else
+      this->write(L"(null)");
+    return this->out();
+  }
+
+  iterator operator()(basic_string_view<char_type> value) {
+    return base::operator()(value);
+  }
+
+  iterator operator()(monostate value) { return base::operator()(value); }
+
+  /** Formats a pointer. */
+  iterator operator()(const void* value) {
+    if (value) return base::operator()(value);
+    this->specs()->type = 0;
+    write_null_pointer(char_type());
+    return this->out();
+  }
+
+  /** Formats an argument of a custom (user-defined) type. */
+  iterator operator()(typename basic_format_arg<context_type>::handle handle) {
+    handle.format(context_.parse_context(), context_);
+    return this->out();
+  }
+};
+
+template <typename T> struct printf_formatter {
+  printf_formatter() = delete;
+
+  template <typename ParseContext>
+  auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename FormatContext>
+  auto format(const T& value, FormatContext& ctx) -> decltype(ctx.out()) {
+    detail::format_value(detail::get_container(ctx.out()), value);
+    return ctx.out();
+  }
+};
+
+/**
+ This template formats data and writes the output through an output iterator.
+ */
+template <typename OutputIt, typename Char> class basic_printf_context {
+ public:
+  /** The character type for the output. */
+  using char_type = Char;
+  using iterator = OutputIt;
+  using format_arg = basic_format_arg<basic_printf_context>;
+  using parse_context_type = basic_printf_parse_context<Char>;
+  template <typename T> using formatter_type = printf_formatter<T>;
+
+ private:
+  using format_specs = basic_format_specs<char_type>;
+
+  OutputIt out_;
+  basic_format_args<basic_printf_context> args_;
+  parse_context_type parse_ctx_;
+
+  static void parse_flags(format_specs& specs, const Char*& it,
+                          const Char* end);
+
+  // Returns the argument with specified index or, if arg_index is -1, the next
+  // argument.
+  format_arg get_arg(int arg_index = -1);
+
+  // Parses argument index, flags and width and returns the argument index.
+  int parse_header(const Char*& it, const Char* end, format_specs& specs);
+
+ public:
+  /**
+   \rst
+   Constructs a ``printf_context`` object. References to the arguments are
+   stored in the context object so make sure they have appropriate lifetimes.
+   \endrst
+   */
+  basic_printf_context(OutputIt out, basic_string_view<char_type> format_str,
+                       basic_format_args<basic_printf_context> args)
+      : out_(out), args_(args), parse_ctx_(format_str) {}
+
+  OutputIt out() { return out_; }
+  void advance_to(OutputIt it) { out_ = it; }
+
+  detail::locale_ref locale() { return {}; }
+
+  format_arg arg(int id) const { return args_.get(id); }
+
+  parse_context_type& parse_context() { return parse_ctx_; }
+
+  FMT_CONSTEXPR void on_error(const char* message) {
+    parse_ctx_.on_error(message);
+  }
+
+  /** Formats stored arguments and writes the output to the range. */
+  template <typename ArgFormatter = printf_arg_formatter<OutputIt, Char>>
+  OutputIt format();
+};
+
+template <typename OutputIt, typename Char>
+void basic_printf_context<OutputIt, Char>::parse_flags(format_specs& specs,
+                                                       const Char*& it,
+                                                       const Char* end) {
+  for (; it != end; ++it) {
+    switch (*it) {
+    case '-':
+      specs.align = align::left;
+      break;
+    case '+':
+      specs.sign = sign::plus;
+      break;
+    case '0':
+      specs.fill[0] = '0';
+      break;
+    case ' ':
+      if (specs.sign != sign::plus) {
+        specs.sign = sign::space;
+      }
+      break;
+    case '#':
+      specs.alt = true;
+      break;
+    default:
+      return;
+    }
+  }
+}
+
+template <typename OutputIt, typename Char>
+typename basic_printf_context<OutputIt, Char>::format_arg
+basic_printf_context<OutputIt, Char>::get_arg(int arg_index) {
+  if (arg_index < 0)
+    arg_index = parse_ctx_.next_arg_id();
+  else
+    parse_ctx_.check_arg_id(--arg_index);
+  return detail::get_arg(*this, arg_index);
+}
+
+template <typename OutputIt, typename Char>
+int basic_printf_context<OutputIt, Char>::parse_header(const Char*& it,
+                                                       const Char* end,
+                                                       format_specs& specs) {
+  int arg_index = -1;
+  char_type c = *it;
+  if (c >= '0' && c <= '9') {
+    // Parse an argument index (if followed by '$') or a width possibly
+    // preceded with '0' flag(s).
+    detail::error_handler eh;
+    int value = parse_nonnegative_int(it, end, eh);
+    if (it != end && *it == '$') {  // value is an argument index
+      ++it;
+      arg_index = value;
+    } else {
+      if (c == '0') specs.fill[0] = '0';
+      if (value != 0) {
+        // Nonzero value means that we parsed width and don't need to
+        // parse it or flags again, so return now.
+        specs.width = value;
+        return arg_index;
+      }
+    }
+  }
+  parse_flags(specs, it, end);
+  // Parse width.
+  if (it != end) {
+    if (*it >= '0' && *it <= '9') {
+      detail::error_handler eh;
+      specs.width = parse_nonnegative_int(it, end, eh);
+    } else if (*it == '*') {
+      ++it;
+      specs.width = static_cast<int>(visit_format_arg(
+          detail::printf_width_handler<char_type>(specs), get_arg()));
+    }
+  }
+  return arg_index;
+}
+
+template <typename OutputIt, typename Char>
+template <typename ArgFormatter>
+OutputIt basic_printf_context<OutputIt, Char>::format() {
+  auto out = this->out();
+  const Char* start = parse_ctx_.begin();
+  const Char* end = parse_ctx_.end();
+  auto it = start;
+  while (it != end) {
+    char_type c = *it++;
+    if (c != '%') continue;
+    if (it != end && *it == c) {
+      out = std::copy(start, it, out);
+      start = ++it;
+      continue;
+    }
+    out = std::copy(start, it - 1, out);
+
+    format_specs specs;
+    specs.align = align::right;
+
+    // Parse argument index, flags and width.
+    int arg_index = parse_header(it, end, specs);
+    if (arg_index == 0) on_error("argument not found");
+
+    // Parse precision.
+    if (it != end && *it == '.') {
+      ++it;
+      c = it != end ? *it : 0;
+      if ('0' <= c && c <= '9') {
+        detail::error_handler eh;
+        specs.precision = parse_nonnegative_int(it, end, eh);
+      } else if (c == '*') {
+        ++it;
+        specs.precision = static_cast<int>(
+            visit_format_arg(detail::printf_precision_handler(), get_arg()));
+      } else {
+        specs.precision = 0;
+      }
+    }
+
+    format_arg arg = get_arg(arg_index);
+    // For d, i, o, u, x, and X conversion specifiers, if a precision is
+    // specified, the '0' flag is ignored
+    if (specs.precision >= 0 && arg.is_integral())
+      specs.fill[0] =
+          ' ';  // Ignore '0' flag for non-numeric types or if '-' present.
+    if (specs.precision >= 0 && arg.type() == detail::type::cstring_type) {
+      auto str = visit_format_arg(detail::get_cstring<Char>(), arg);
+      auto str_end = str + specs.precision;
+      auto nul = std::find(str, str_end, Char());
+      arg = detail::make_arg<basic_printf_context>(basic_string_view<Char>(
+          str,
+          detail::to_unsigned(nul != str_end ? nul - str : specs.precision)));
+    }
+    if (specs.alt && visit_format_arg(detail::is_zero_int(), arg))
+      specs.alt = false;
+    if (specs.fill[0] == '0') {
+      if (arg.is_arithmetic() && specs.align != align::left)
+        specs.align = align::numeric;
+      else
+        specs.fill[0] = ' ';  // Ignore '0' flag for non-numeric types or if '-'
+                              // flag is also present.
+    }
+
+    // Parse length and convert the argument to the required type.
+    c = it != end ? *it++ : 0;
+    char_type t = it != end ? *it : 0;
+    using detail::convert_arg;
+    switch (c) {
+    case 'h':
+      if (t == 'h') {
+        ++it;
+        t = it != end ? *it : 0;
+        convert_arg<signed char>(arg, t);
+      } else {
+        convert_arg<short>(arg, t);
+      }
+      break;
+    case 'l':
+      if (t == 'l') {
+        ++it;
+        t = it != end ? *it : 0;
+        convert_arg<long long>(arg, t);
+      } else {
+        convert_arg<long>(arg, t);
+      }
+      break;
+    case 'j':
+      convert_arg<intmax_t>(arg, t);
+      break;
+    case 'z':
+      convert_arg<size_t>(arg, t);
+      break;
+    case 't':
+      convert_arg<std::ptrdiff_t>(arg, t);
+      break;
+    case 'L':
+      // printf produces garbage when 'L' is omitted for long double, no
+      // need to do the same.
+      break;
+    default:
+      --it;
+      convert_arg<void>(arg, c);
+    }
+
+    // Parse type.
+    if (it == end) FMT_THROW(format_error("invalid format string"));
+    specs.type = static_cast<char>(*it++);
+    if (arg.is_integral()) {
+      // Normalize type.
+      switch (specs.type) {
+      case 'i':
+      case 'u':
+        specs.type = 'd';
+        break;
+      case 'c':
+        visit_format_arg(detail::char_converter<basic_printf_context>(arg),
+                         arg);
+        break;
+      }
+    }
+
+    start = it;
+
+    // Format argument.
+    out = visit_format_arg(ArgFormatter(out, specs, *this), arg);
+  }
+  return std::copy(start, it, out);
+}
+
+template <typename Char>
+using basic_printf_context_t =
+    basic_printf_context<std::back_insert_iterator<detail::buffer<Char>>, Char>;
+
+using printf_context = basic_printf_context_t<char>;
+using wprintf_context = basic_printf_context_t<wchar_t>;
+
+using printf_args = basic_format_args<printf_context>;
+using wprintf_args = basic_format_args<wprintf_context>;
+
+/**
+  \rst
+  Constructs an `~fmt::format_arg_store` object that contains references to
+  arguments and can be implicitly converted to `~fmt::printf_args`.
+  \endrst
+ */
+template <typename... Args>
+inline format_arg_store<printf_context, Args...> make_printf_args(
+    const Args&... args) {
+  return {args...};
+}
+
+/**
+  \rst
+  Constructs an `~fmt::format_arg_store` object that contains references to
+  arguments and can be implicitly converted to `~fmt::wprintf_args`.
+  \endrst
+ */
+template <typename... Args>
+inline format_arg_store<wprintf_context, Args...> make_wprintf_args(
+    const Args&... args) {
+  return {args...};
+}
+
+template <typename S, typename Char = char_t<S>>
+inline std::basic_string<Char> vsprintf(
+    const S& format,
+    basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args) {
+  basic_memory_buffer<Char> buffer;
+  vprintf(buffer, to_string_view(format), args);
+  return to_string(buffer);
+}
+
+/**
+  \rst
+  Formats arguments and returns the result as a string.
+
+  **Example**::
+
+    std::string message = fmt::sprintf("The answer is %d", 42);
+  \endrst
+*/
+template <typename S, typename... Args,
+          typename Char = enable_if_t<detail::is_string<S>::value, char_t<S>>>
+inline std::basic_string<Char> sprintf(const S& format, const Args&... args) {
+  using context = basic_printf_context_t<Char>;
+  return vsprintf(to_string_view(format), make_format_args<context>(args...));
+}
+
+template <typename S, typename Char = char_t<S>>
+inline int vfprintf(
+    std::FILE* f, const S& format,
+    basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args) {
+  basic_memory_buffer<Char> buffer;
+  vprintf(buffer, to_string_view(format), args);
+  size_t size = buffer.size();
+  return std::fwrite(buffer.data(), sizeof(Char), size, f) < size
+             ? -1
+             : static_cast<int>(size);
+}
+
+/**
+  \rst
+  Prints formatted data to the file *f*.
+
+  **Example**::
+
+    fmt::fprintf(stderr, "Don't %s!", "panic");
+  \endrst
+ */
+template <typename S, typename... Args,
+          typename Char = enable_if_t<detail::is_string<S>::value, char_t<S>>>
+inline int fprintf(std::FILE* f, const S& format, const Args&... args) {
+  using context = basic_printf_context_t<Char>;
+  return vfprintf(f, to_string_view(format),
+                  make_format_args<context>(args...));
+}
+
+template <typename S, typename Char = char_t<S>>
+inline int vprintf(
+    const S& format,
+    basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args) {
+  return vfprintf(stdout, to_string_view(format), args);
+}
+
+/**
+  \rst
+  Prints formatted data to ``stdout``.
+
+  **Example**::
+
+    fmt::printf("Elapsed time: %.2f seconds", 1.23);
+  \endrst
+ */
+template <typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_string<S>::value)>
+inline int printf(const S& format_str, const Args&... args) {
+  using context = basic_printf_context_t<char_t<S>>;
+  return vprintf(to_string_view(format_str),
+                 make_format_args<context>(args...));
+}
+
+template <typename S, typename Char = char_t<S>>
+inline int vfprintf(
+    std::basic_ostream<Char>& os, const S& format,
+    basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args) {
+  basic_memory_buffer<Char> buffer;
+  vprintf(buffer, to_string_view(format), args);
+  detail::write_buffer(os, buffer);
+  return static_cast<int>(buffer.size());
+}
+
+/** Formats arguments and writes the output to the range. */
+template <typename ArgFormatter, typename Char,
+          typename Context =
+              basic_printf_context<typename ArgFormatter::iterator, Char>>
+typename ArgFormatter::iterator vprintf(
+    detail::buffer<Char>& out, basic_string_view<Char> format_str,
+    basic_format_args<type_identity_t<Context>> args) {
+  typename ArgFormatter::iterator iter(out);
+  Context(iter, format_str, args).template format<ArgFormatter>();
+  return iter;
+}
+
+/**
+  \rst
+  Prints formatted data to the stream *os*.
+
+  **Example**::
+
+    fmt::fprintf(cerr, "Don't %s!", "panic");
+  \endrst
+ */
+template <typename S, typename... Args, typename Char = char_t<S>>
+inline int fprintf(std::basic_ostream<Char>& os, const S& format_str,
+                   const Args&... args) {
+  using context = basic_printf_context_t<Char>;
+  return vfprintf(os, to_string_view(format_str),
+                  make_format_args<context>(args...));
+}
+FMT_END_NAMESPACE
+
+#endif  // FMT_PRINTF_H_
diff --git a/external/fmtlib/include/fmt/ranges.h b/external/fmtlib/include/fmt/ranges.h
new file mode 100644
index 000000000..c48f1727d
--- /dev/null
+++ b/external/fmtlib/include/fmt/ranges.h
@@ -0,0 +1,386 @@
+// Formatting library for C++ - experimental range support
+//
+// Copyright (c) 2012 - present, Victor Zverovich
+// All rights reserved.
+//
+// For the license information refer to format.h.
+//
+// Copyright (c) 2018 - present, Remotion (Igor Schulz)
+// All Rights Reserved
+// {fmt} support for ranges, containers and types tuple interface.
+
+#ifndef FMT_RANGES_H_
+#define FMT_RANGES_H_
+
+#include <initializer_list>
+#include <type_traits>
+
+#include "format.h"
+
+// output only up to N items from the range.
+#ifndef FMT_RANGE_OUTPUT_LENGTH_LIMIT
+#  define FMT_RANGE_OUTPUT_LENGTH_LIMIT 256
+#endif
+
+FMT_BEGIN_NAMESPACE
+
+template <typename Char> struct formatting_base {
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+};
+
+template <typename Char, typename Enable = void>
+struct formatting_range : formatting_base<Char> {
+  static FMT_CONSTEXPR_DECL const size_t range_length_limit =
+      FMT_RANGE_OUTPUT_LENGTH_LIMIT;  // output only up to N items from the
+                                      // range.
+  Char prefix;
+  Char delimiter;
+  Char postfix;
+  formatting_range() : prefix('{'), delimiter(','), postfix('}') {}
+  static FMT_CONSTEXPR_DECL const bool add_delimiter_spaces = true;
+  static FMT_CONSTEXPR_DECL const bool add_prepostfix_space = false;
+};
+
+template <typename Char, typename Enable = void>
+struct formatting_tuple : formatting_base<Char> {
+  Char prefix;
+  Char delimiter;
+  Char postfix;
+  formatting_tuple() : prefix('('), delimiter(','), postfix(')') {}
+  static FMT_CONSTEXPR_DECL const bool add_delimiter_spaces = true;
+  static FMT_CONSTEXPR_DECL const bool add_prepostfix_space = false;
+};
+
+namespace detail {
+
+template <typename RangeT, typename OutputIterator>
+OutputIterator copy(const RangeT& range, OutputIterator out) {
+  for (auto it = range.begin(), end = range.end(); it != end; ++it)
+    *out++ = *it;
+  return out;
+}
+
+template <typename OutputIterator>
+OutputIterator copy(const char* str, OutputIterator out) {
+  while (*str) *out++ = *str++;
+  return out;
+}
+
+template <typename OutputIterator>
+OutputIterator copy(char ch, OutputIterator out) {
+  *out++ = ch;
+  return out;
+}
+
+/// Return true value if T has std::string interface, like std::string_view.
+template <typename T> class is_like_std_string {
+  template <typename U>
+  static auto check(U* p)
+      -> decltype((void)p->find('a'), p->length(), (void)p->data(), int());
+  template <typename> static void check(...);
+
+ public:
+  static FMT_CONSTEXPR_DECL const bool value =
+      is_string<T>::value || !std::is_void<decltype(check<T>(nullptr))>::value;
+};
+
+template <typename Char>
+struct is_like_std_string<fmt::basic_string_view<Char>> : std::true_type {};
+
+template <typename... Ts> struct conditional_helper {};
+
+template <typename T, typename _ = void> struct is_range_ : std::false_type {};
+
+#if !FMT_MSC_VER || FMT_MSC_VER > 1800
+template <typename T>
+struct is_range_<
+    T, conditional_t<false,
+                     conditional_helper<decltype(std::declval<T>().begin()),
+                                        decltype(std::declval<T>().end())>,
+                     void>> : std::true_type {};
+#endif
+
+/// tuple_size and tuple_element check.
+template <typename T> class is_tuple_like_ {
+  template <typename U>
+  static auto check(U* p) -> decltype(std::tuple_size<U>::value, int());
+  template <typename> static void check(...);
+
+ public:
+  static FMT_CONSTEXPR_DECL const bool value =
+      !std::is_void<decltype(check<T>(nullptr))>::value;
+};
+
+// Check for integer_sequence
+#if defined(__cpp_lib_integer_sequence) || FMT_MSC_VER >= 1900
+template <typename T, T... N>
+using integer_sequence = std::integer_sequence<T, N...>;
+template <size_t... N> using index_sequence = std::index_sequence<N...>;
+template <size_t N> using make_index_sequence = std::make_index_sequence<N>;
+#else
+template <typename T, T... N> struct integer_sequence {
+  using value_type = T;
+
+  static FMT_CONSTEXPR size_t size() { return sizeof...(N); }
+};
+
+template <size_t... N> using index_sequence = integer_sequence<size_t, N...>;
+
+template <typename T, size_t N, T... Ns>
+struct make_integer_sequence : make_integer_sequence<T, N - 1, N - 1, Ns...> {};
+template <typename T, T... Ns>
+struct make_integer_sequence<T, 0, Ns...> : integer_sequence<T, Ns...> {};
+
+template <size_t N>
+using make_index_sequence = make_integer_sequence<size_t, N>;
+#endif
+
+template <class Tuple, class F, size_t... Is>
+void for_each(index_sequence<Is...>, Tuple&& tup, F&& f) FMT_NOEXCEPT {
+  using std::get;
+  // using free function get<I>(T) now.
+  const int _[] = {0, ((void)f(get<Is>(tup)), 0)...};
+  (void)_;  // blocks warnings
+}
+
+template <class T>
+FMT_CONSTEXPR make_index_sequence<std::tuple_size<T>::value> get_indexes(
+    T const&) {
+  return {};
+}
+
+template <class Tuple, class F> void for_each(Tuple&& tup, F&& f) {
+  const auto indexes = get_indexes(tup);
+  for_each(indexes, std::forward<Tuple>(tup), std::forward<F>(f));
+}
+
+template <typename Arg, FMT_ENABLE_IF(!is_like_std_string<
+                                      typename std::decay<Arg>::type>::value)>
+FMT_CONSTEXPR const char* format_str_quoted(bool add_space, const Arg&) {
+  return add_space ? " {}" : "{}";
+}
+
+template <typename Arg, FMT_ENABLE_IF(is_like_std_string<
+                                      typename std::decay<Arg>::type>::value)>
+FMT_CONSTEXPR const char* format_str_quoted(bool add_space, const Arg&) {
+  return add_space ? " \"{}\"" : "\"{}\"";
+}
+
+FMT_CONSTEXPR const char* format_str_quoted(bool add_space, const char*) {
+  return add_space ? " \"{}\"" : "\"{}\"";
+}
+FMT_CONSTEXPR const wchar_t* format_str_quoted(bool add_space, const wchar_t*) {
+  return add_space ? L" \"{}\"" : L"\"{}\"";
+}
+
+FMT_CONSTEXPR const char* format_str_quoted(bool add_space, const char) {
+  return add_space ? " '{}'" : "'{}'";
+}
+FMT_CONSTEXPR const wchar_t* format_str_quoted(bool add_space, const wchar_t) {
+  return add_space ? L" '{}'" : L"'{}'";
+}
+
+}  // namespace detail
+
+template <typename T> struct is_tuple_like {
+  static FMT_CONSTEXPR_DECL const bool value =
+      detail::is_tuple_like_<T>::value && !detail::is_range_<T>::value;
+};
+
+template <typename TupleT, typename Char>
+struct formatter<TupleT, Char, enable_if_t<fmt::is_tuple_like<TupleT>::value>> {
+ private:
+  // C++11 generic lambda for format()
+  template <typename FormatContext> struct format_each {
+    template <typename T> void operator()(const T& v) {
+      if (i > 0) {
+        if (formatting.add_prepostfix_space) {
+          *out++ = ' ';
+        }
+        out = detail::copy(formatting.delimiter, out);
+      }
+      out = format_to(out,
+                      detail::format_str_quoted(
+                          (formatting.add_delimiter_spaces && i > 0), v),
+                      v);
+      ++i;
+    }
+
+    formatting_tuple<Char>& formatting;
+    size_t& i;
+    typename std::add_lvalue_reference<decltype(
+        std::declval<FormatContext>().out())>::type out;
+  };
+
+ public:
+  formatting_tuple<Char> formatting;
+
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return formatting.parse(ctx);
+  }
+
+  template <typename FormatContext = format_context>
+  auto format(const TupleT& values, FormatContext& ctx) -> decltype(ctx.out()) {
+    auto out = ctx.out();
+    size_t i = 0;
+    detail::copy(formatting.prefix, out);
+
+    detail::for_each(values, format_each<FormatContext>{formatting, i, out});
+    if (formatting.add_prepostfix_space) {
+      *out++ = ' ';
+    }
+    detail::copy(formatting.postfix, out);
+
+    return ctx.out();
+  }
+};
+
+template <typename T, typename Char> struct is_range {
+  static FMT_CONSTEXPR_DECL const bool value =
+      detail::is_range_<T>::value && !detail::is_like_std_string<T>::value &&
+      !std::is_convertible<T, std::basic_string<Char>>::value &&
+      !std::is_constructible<detail::std_string_view<Char>, T>::value;
+};
+
+template <typename RangeT, typename Char>
+struct formatter<RangeT, Char,
+                 enable_if_t<fmt::is_range<RangeT, Char>::value>> {
+  formatting_range<Char> formatting;
+
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return formatting.parse(ctx);
+  }
+
+  template <typename FormatContext>
+  typename FormatContext::iterator format(const RangeT& values,
+                                          FormatContext& ctx) {
+    auto out = detail::copy(formatting.prefix, ctx.out());
+    size_t i = 0;
+    auto it = values.begin();
+    auto end = values.end();
+    for (; it != end; ++it) {
+      if (i > 0) {
+        if (formatting.add_prepostfix_space) *out++ = ' ';
+        out = detail::copy(formatting.delimiter, out);
+      }
+      out = format_to(out,
+                      detail::format_str_quoted(
+                          (formatting.add_delimiter_spaces && i > 0), *it),
+                      *it);
+      if (++i > formatting.range_length_limit) {
+        out = format_to(out, " ... <other elements>");
+        break;
+      }
+    }
+    if (formatting.add_prepostfix_space) *out++ = ' ';
+    return detail::copy(formatting.postfix, out);
+  }
+};
+
+template <typename Char, typename... T> struct tuple_arg_join : detail::view {
+  const std::tuple<T...>& tuple;
+  basic_string_view<Char> sep;
+
+  tuple_arg_join(const std::tuple<T...>& t, basic_string_view<Char> s)
+      : tuple{t}, sep{s} {}
+};
+
+template <typename Char, typename... T>
+struct formatter<tuple_arg_join<Char, T...>, Char> {
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename FormatContext>
+  typename FormatContext::iterator format(
+      const tuple_arg_join<Char, T...>& value, FormatContext& ctx) {
+    return format(value, ctx, detail::make_index_sequence<sizeof...(T)>{});
+  }
+
+ private:
+  template <typename FormatContext, size_t... N>
+  typename FormatContext::iterator format(
+      const tuple_arg_join<Char, T...>& value, FormatContext& ctx,
+      detail::index_sequence<N...>) {
+    return format_args(value, ctx, std::get<N>(value.tuple)...);
+  }
+
+  template <typename FormatContext>
+  typename FormatContext::iterator format_args(
+      const tuple_arg_join<Char, T...>&, FormatContext& ctx) {
+    // NOTE: for compilers that support C++17, this empty function instantiation
+    // can be replaced with a constexpr branch in the variadic overload.
+    return ctx.out();
+  }
+
+  template <typename FormatContext, typename Arg, typename... Args>
+  typename FormatContext::iterator format_args(
+      const tuple_arg_join<Char, T...>& value, FormatContext& ctx,
+      const Arg& arg, const Args&... args) {
+    using base = formatter<typename std::decay<Arg>::type, Char>;
+    auto out = ctx.out();
+    out = base{}.format(arg, ctx);
+    if (sizeof...(Args) > 0) {
+      out = std::copy(value.sep.begin(), value.sep.end(), out);
+      ctx.advance_to(out);
+      return format_args(value, ctx, args...);
+    }
+    return out;
+  }
+};
+
+/**
+  \rst
+  Returns an object that formats `tuple` with elements separated by `sep`.
+
+  **Example**::
+
+    std::tuple<int, char> t = {1, 'a'};
+    fmt::print("{}", fmt::join(t, ", "));
+    // Output: "1, a"
+  \endrst
+ */
+template <typename... T>
+FMT_CONSTEXPR tuple_arg_join<char, T...> join(const std::tuple<T...>& tuple,
+                                              string_view sep) {
+  return {tuple, sep};
+}
+
+template <typename... T>
+FMT_CONSTEXPR tuple_arg_join<wchar_t, T...> join(const std::tuple<T...>& tuple,
+                                                 wstring_view sep) {
+  return {tuple, sep};
+}
+
+/**
+  \rst
+  Returns an object that formats `initializer_list` with elements separated by
+  `sep`.
+
+  **Example**::
+
+    fmt::print("{}", fmt::join({1, 2, 3}, ", "));
+    // Output: "1, 2, 3"
+  \endrst
+ */
+template <typename T>
+arg_join<const T*, const T*, char> join(std::initializer_list<T> list,
+                                        string_view sep) {
+  return join(std::begin(list), std::end(list), sep);
+}
+
+template <typename T>
+arg_join<const T*, const T*, wchar_t> join(std::initializer_list<T> list,
+                                           wstring_view sep) {
+  return join(std::begin(list), std::end(list), sep);
+}
+
+FMT_END_NAMESPACE
+
+#endif  // FMT_RANGES_H_
diff --git a/opm/simulators/utils/readDeck.cpp b/opm/simulators/utils/readDeck.cpp
index bd1f602b9..0a4ac6898 100644
--- a/opm/simulators/utils/readDeck.cpp
+++ b/opm/simulators/utils/readDeck.cpp
@@ -42,6 +42,8 @@
 #include <opm/simulators/utils/ParallelEclipseState.hpp>
 #include <opm/simulators/utils/ParallelSerialization.hpp>
 
+#include <fmt/format.h>
+
 #include <cstdlib>
 
 namespace Opm
@@ -54,7 +56,7 @@ void ensureOutputDirExists_(const std::string& cmdline_output_dir)
             Opm::filesystem::create_directories(cmdline_output_dir);
         }
         catch (...) {
-            throw std::runtime_error("Creation of output directory '" + cmdline_output_dir + "' failed\n");
+            throw std::runtime_error(fmt::format("Creation of output directory '{}' failed\n", cmdline_output_dir));
         }
     }
 }