Merge pull request #16553 from seandewar/vim-8.2.0878

vim-patch:8.2.{0882,1051,1083}: port `reduce()` function

runtime/doc/builtin.txt

@@ -340,6 +340,8 @@ range({expr} [, {max} [, {stride}]])
 readdir({dir} [, {expr}])	List	file names in {dir} selected by {expr}
 readfile({fname} [, {type} [, {max}]])
 				List	get list of lines from file {fname}
+reduce({object}, {func} [, {initial}])
+				any	reduce {object} using {func}
 reg_executing()			String	get the executing register name
 reg_recorded()			String	get the last recorded register name
 reg_recording()			String	get the recording register name
@@ -5772,6 +5774,25 @@ readfile({fname} [, {type} [, {max}]])
 		Can also be used as a |method|: >
 			GetFileName()->readfile()
 
+reduce({object}, {func} [, {initial}])			*reduce()* *E998*
+		{func} is called for every item in {object}, which can be a
+		|List| or a |Blob|.  {func} is called with two arguments: the
+		result so far and current item.  After processing all items
+		the result is returned.
+
+		{initial} is the initial result.  When omitted, the first item
+		in {object} is used and {func} is first called for the second
+		item.  If {initial} is not given and {object} is empty no
+		result can be computed, an E998 error is given.
+
+		Examples: >
+			echo reduce([1, 3, 5], { acc, val -> acc + val })
+			echo reduce(['x', 'y'], { acc, val -> acc .. val }, 'a')
+			echo reduce(0z1122, { acc, val -> 2 * acc + val })
+<
+		Can also be used as a |method|: >
+			echo mylist->reduce({ acc, val -> acc + val }, 0)
+
 reg_executing()						*reg_executing()*
 		Returns the single letter name of the register being executed.
 		Returns an empty string when no register is being executed.

src/nvim/eval.lua

@@ -282,6 +282,7 @@ return {
     range={args={1, 3}, base=1},
     readdir={args={1, 2}, base=1},
     readfile={args={1, 3}, base=1},
+    reduce={args={2, 3}, base=1},
     reg_executing={},
     reg_recording={},
     reg_recorded={},

src/nvim/eval/funcs.c

@@ -100,6 +100,7 @@ PRAGMA_DIAG_POP
 
 static char *e_listblobarg = N_("E899: Argument of %s must be a List or Blob");
 static char *e_invalwindow = N_("E957: Invalid window number");
+static char *e_reduceempty = N_("E998: Reduce of an empty %s with no initial value");
 
 /// Dummy va_list for passing to vim_snprintf
 ///
@@ -8054,6 +8055,102 @@ static void f_reverse(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   }
 }
 
+/// "reduce(list, { accumlator, element -> value } [, initial])" function
+static void f_reduce(typval_T *argvars, typval_T *rettv, FunPtr fptr)
+{
+  if (argvars[0].v_type != VAR_LIST && argvars[0].v_type != VAR_BLOB) {
+    emsg(_(e_listblobreq));
+    return;
+  }
+
+  const char_u *func_name;
+  partial_T *partial = NULL;
+  if (argvars[1].v_type == VAR_FUNC) {
+    func_name = argvars[1].vval.v_string;
+  } else if (argvars[1].v_type == VAR_PARTIAL) {
+    partial = argvars[1].vval.v_partial;
+    func_name = partial_name(partial);
+  } else {
+    func_name = (const char_u *)tv_get_string(&argvars[1]);
+  }
+  if (*func_name == NUL) {
+    return;  // type error or empty name
+  }
+
+  funcexe_T funcexe = FUNCEXE_INIT;
+  funcexe.evaluate = true;
+  funcexe.partial = partial;
+
+  typval_T initial;
+  typval_T argv[3];
+  if (argvars[0].v_type == VAR_LIST) {
+    list_T *const l = argvars[0].vval.v_list;
+    const listitem_T *li;
+
+    if (argvars[2].v_type == VAR_UNKNOWN) {
+      if (tv_list_len(l) == 0) {
+        semsg(_(e_reduceempty), "List");
+        return;
+      }
+      const listitem_T *const first = tv_list_first(l);
+      initial = *TV_LIST_ITEM_TV(first);
+      li = TV_LIST_ITEM_NEXT(l, first);
+    } else {
+      initial = argvars[2];
+      li = tv_list_first(l);
+    }
+
+    tv_copy(&initial, rettv);
+
+    if (l != NULL) {
+      const VarLockStatus prev_locked = tv_list_locked(l);
+      const int called_emsg_start = called_emsg;
+
+      tv_list_set_lock(l, VAR_FIXED);  // disallow the list changing here
+      for (; li != NULL; li = TV_LIST_ITEM_NEXT(l, li)) {
+        argv[0] = *rettv;
+        argv[1] = *TV_LIST_ITEM_TV(li);
+        rettv->v_type = VAR_UNKNOWN;
+        const int r = call_func(func_name, -1, rettv, 2, argv, &funcexe);
+        tv_clear(&argv[0]);
+        if (r == FAIL || called_emsg != called_emsg_start) {
+          break;
+        }
+      }
+      tv_list_set_lock(l, prev_locked);
+    }
+  } else {
+    const blob_T *const b = argvars[0].vval.v_blob;
+    int i;
+
+    if (argvars[2].v_type == VAR_UNKNOWN) {
+      if (tv_blob_len(b) == 0) {
+        semsg(_(e_reduceempty), "Blob");
+        return;
+      }
+      initial.v_type = VAR_NUMBER;
+      initial.vval.v_number = tv_blob_get(b, 0);
+      i = 1;
+    } else if (argvars[2].v_type != VAR_NUMBER) {
+      emsg(_(e_number_exp));
+      return;
+    } else {
+      initial = argvars[2];
+      i = 0;
+    }
+
+    tv_copy(&initial, rettv);
+    for (; i < tv_blob_len(b); i++) {
+      argv[0] = *rettv;
+      argv[1].v_type = VAR_NUMBER;
+      argv[1].vval.v_number = tv_blob_get(b, i);
+      if (call_func(func_name, -1, rettv, 2, argv, &funcexe) == FAIL) {
+        return;
+      }
+    }
+  }
+}
+
 #define SP_NOMOVE       0x01        ///< don't move cursor
 #define SP_REPEAT       0x02        ///< repeat to find outer pair
 #define SP_RETCOUNT     0x04        ///< return matchcount

src/nvim/testdir/test_listdict.vim

@@ -620,6 +620,49 @@ func Test_reverse_sort_uniq()
   call assert_fails('call reverse("")', 'E899:')
 endfunc
 
+" reduce a list or a blob
+func Test_reduce()
+  call assert_equal(1, reduce([], { acc, val -> acc + val }, 1))
+  call assert_equal(10, reduce([1, 3, 5], { acc, val -> acc + val }, 1))
+  call assert_equal(2 * (2 * ((2 * 1) + 2) + 3) + 4, reduce([2, 3, 4], { acc, val -> 2 * acc + val }, 1))
+  call assert_equal('a x y z', ['x', 'y', 'z']->reduce({ acc, val -> acc .. ' ' .. val}, 'a'))
+  call assert_equal(#{ x: 1, y: 1, z: 1 }, ['x', 'y', 'z']->reduce({ acc, val -> extend(acc, { val: 1 }) }, {}))
+  call assert_equal([0, 1, 2, 3], reduce([1, 2, 3], function('add'), [0]))
+
+  let l = ['x', 'y', 'z']
+  call assert_equal(42, reduce(l, function('get'), #{ x: #{ y: #{ z: 42 } } }))
+  call assert_equal(['x', 'y', 'z'], l)
+
+  call assert_equal(1, reduce([1], { acc, val -> acc + val }))
+  call assert_equal('x y z', reduce(['x', 'y', 'z'], { acc, val -> acc .. ' ' .. val }))
+  call assert_equal(120, range(1, 5)->reduce({ acc, val -> acc * val }))
+  call assert_fails("call reduce([], { acc, val -> acc + val })", 'E998: Reduce of an empty List with no initial value')
+
+  call assert_equal(1, reduce(0z, { acc, val -> acc + val }, 1))
+  call assert_equal(1 + 0xaf + 0xbf + 0xcf, reduce(0zAFBFCF, { acc, val -> acc + val }, 1))
+  call assert_equal(2 * (2 * 1 + 0xaf) + 0xbf, 0zAFBF->reduce({ acc, val -> 2 * acc + val }, 1))
+
+  call assert_equal(0xff, reduce(0zff, { acc, val -> acc + val }))
+  call assert_equal(2 * (2 * 0xaf + 0xbf) + 0xcf, reduce(0zAFBFCF, { acc, val -> 2 * acc + val }))
+  call assert_fails("call reduce(0z, { acc, val -> acc + val })", 'E998: Reduce of an empty Blob with no initial value')
+
+  call assert_fails("call reduce({}, { acc, val -> acc + val }, 1)", 'E897:')
+  call assert_fails("call reduce(0, { acc, val -> acc + val }, 1)", 'E897:')
+  call assert_fails("call reduce('', { acc, val -> acc + val }, 1)", 'E897:')
+
+  let g:lut = [1, 2, 3, 4]
+  func EvilRemove()
+    call remove(g:lut, 1)
+    return 1
+  endfunc
+  call assert_fails("call reduce(g:lut, { acc, val -> EvilRemove() }, 1)", 'E742:')
+  unlet g:lut
+  delfunc EvilRemove
+
+  call assert_equal(42, reduce(v:_null_list, function('add'), 42))
+  call assert_equal(42, reduce(v:_null_blob, function('add'), 42))
+endfunc
+
 " splitting a string to a List
 func Test_str_split()
   call assert_equal(['aa', 'bb'], split('  aa  bb '))