vim-patch:7.4.1730

Problem:    It is not easy to get a character out of a string.
Solution:   Add strgetchar() and strcharpart().

58de0e2dcc

src/nvim/eval.c

@@ -15612,6 +15612,39 @@ static void f_strftime(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   }
 }
 
+// "strgetchar()" function
+static void f_strgetchar(typval_T *argvars, typval_T *rettv, FunPtr fptr)
+{
+  char_u *str;
+  int len;
+  int error = false;
+  int charidx;
+
+  rettv->vval.v_number = -1;
+  str = get_tv_string_chk(&argvars[0]);
+  if (str == NULL) {
+    return;
+  }
+  len = (int)STRLEN(str);
+  charidx = get_tv_number_chk(&argvars[1], &error);
+  if (error) {
+    return;
+  }
+
+  {
+    int byteidx = 0;
+
+    while (charidx >= 0 && byteidx < len) {
+      if (charidx == 0) {
+        rettv->vval.v_number = mb_ptr2char(str + byteidx);
+        break;
+      }
+      charidx--;
+      byteidx += mb_char2len(str[byteidx]);
+    }
+  }
+}
+
 /*
  * "stridx()" function
  */
@@ -15712,6 +15745,58 @@ static void f_strwidth(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   rettv->vval.v_number = (varnumber_T) mb_string2cells(s);
 }
 
+// "strcharpart()" function
+static void f_strcharpart(typval_T *argvars, typval_T *rettv, FunPtr fptr) {
+  char_u *p;
+  int nchar;
+  int nbyte = 0;
+  int charlen;
+  int len = 0;
+  int slen;
+  int error = false;
+
+  p = get_tv_string(&argvars[0]);
+  slen = (int)STRLEN(p);
+
+  nchar = get_tv_number_chk(&argvars[1], &error);
+  if (!error) {
+    if (nchar > 0) {
+      while (nchar > 0 && nbyte < slen) {
+        nbyte += mb_char2len(p[nbyte]);
+        nchar--;
+      }
+    } else {
+      nbyte = nchar;
+    }
+  }
+  if (argvars[2].v_type != VAR_UNKNOWN) {
+    charlen = get_tv_number(&argvars[2]);
+    while (charlen > 0 && nbyte + len < slen) {
+      len += mb_char2len(p[nbyte + len]);
+      charlen--;
+    }
+  } else {
+    len = slen - nbyte;    // default: all bytes that are available.
+  }
+
+  // Only return the overlap between the specified part and the actual
+  // string.
+  if (nbyte < 0) {
+    len += nbyte;
+    nbyte = 0;
+  } else if (nbyte > slen) {
+    nbyte = slen;
+  }
+  if (len < 0) {
+    len = 0;
+  } else if (nbyte + len > slen) {
+    len = slen - nbyte;
+  }
+
+  rettv->v_type = VAR_STRING;
+  rettv->vval.v_string = vim_strnsave(p + nbyte, len);
+}
+
 /*
  * "strpart()" function
  */

src/nvim/eval.lua

@@ -268,9 +268,11 @@ return {
     sqrt={args=1, func="float_op_wrapper", data="&sqrt"},
     str2float={args=1},
     str2nr={args={1, 2}},
+    strcharpart={args={2, 3}},
     strchars={args={1,2}},
     strdisplaywidth={args={1, 2}},
     strftime={args={1, 2}},
+    strgetchar={args={2,2}},
     stridx={args={2, 3}},
     string={args=1},
     strlen={args=1},

src/nvim/testdir/test_alot.vim

@@ -4,6 +4,7 @@
 source test_assign.vim
 source test_cursor_func.vim
 source test_ex_undo.vim
+source test_expr.vim
 source test_feedkeys.vim
 source test_cmdline.vim
 source test_menu.vim

src/nvim/testdir/test_expr.vim

@@ -0,0 +1,48 @@
+" Tests for expressions.
+
+func Test_strgetchar()
+  call assert_equal(char2nr('a'), strgetchar('axb', 0))
+  call assert_equal(char2nr('x'), strgetchar('axb', 1))
+  call assert_equal(char2nr('b'), strgetchar('axb', 2))
+
+  call assert_equal(-1, strgetchar('axb', -1))
+  call assert_equal(-1, strgetchar('axb', 3))
+  call assert_equal(-1, strgetchar('', 0))
+
+  if !has('multi_byte')
+    return
+  endif
+
+  call assert_equal(char2nr('á'), strgetchar('áxb', 0))
+  call assert_equal(char2nr('x'), strgetchar('áxb', 1))
+
+  call assert_equal(char2nr('a'), strgetchar('àxb', 0))
+  call assert_equal(char2nr(''), strgetchar('àxb', 1))
+  call assert_equal(char2nr('x'), strgetchar('àxb', 2))
+endfunc
+
+func Test_strcharpart()
+  call assert_equal('a', strcharpart('axb', 0, 1))
+  call assert_equal('x', strcharpart('axb', 1, 1))
+  call assert_equal('b', strcharpart('axb', 2, 1))
+  call assert_equal('xb', strcharpart('axb', 1))
+
+  call assert_equal('', strcharpart('axb', 1, 0))
+  call assert_equal('', strcharpart('axb', 1, -1))
+  call assert_equal('', strcharpart('axb', -1, 1))
+  call assert_equal('', strcharpart('axb', -2, 2))
+
+  call assert_equal('a', strcharpart('axb', -1, 2))
+
+  if !has('multi_byte')
+    return
+  endif
+
+  call assert_equal('áxb', strcharpart('áxb', 0))
+  call assert_equal('á', strcharpart('áxb', 0, 1))
+  call assert_equal('x', strcharpart('áxb', 1, 1))
+
+  call assert_equal('a', strcharpart('àxb', 0, 1))
+  call assert_equal('', strcharpart('àxb', 1, 1))
+  call assert_equal('x', strcharpart('àxb', 2, 1))
+endfunc

src/nvim/version.c

@@ -713,7 +713,7 @@ static int included_patches[] = {
   // 1733 NA
   1732,
   // 1731,
-  // 1730,
+  1730,
   // 1729 NA
   1728,
   // 1727,