patch 8.2.2344: using inclusive index for slice is not always desired

Problem:    Using inclusive index for slice is not always desired.
Solution:   Add the slice() method, which has an exclusive index. (closes
            #7408)

runtime/doc/eval.txt

@@ -314,6 +314,9 @@ similar to -1. >
 	:let shortlist = mylist[2:2]	" List with one item: [3]
 	:let otherlist = mylist[:]	" make a copy of the List
 
+Notice that the last index is inclusive.  If you prefer using an exclusive
+index use the |slice()| method.
+
 If the first index is beyond the last item of the List or the second item is
 before the first item, the result is an empty list.  There is no error
 message.
@@ -1217,6 +1220,9 @@ a Number it is first converted to a String.
 In Vim9 script the indexes are character indexes.  To use byte indexes use
 |strpart()|.
 
+The item at index expr1b is included, it is inclusive.  For an exclusive index
+use the |slice()| function.
+
 If expr1a is omitted zero is used.  If expr1b is omitted the length of the
 string minus one is used.
 
@@ -2884,6 +2890,8 @@ sign_unplacelist({list})	List	unplace a list of signs
 simplify({filename})		String	simplify filename as much as possible
 sin({expr})			Float	sine of {expr}
 sinh({expr})			Float	hyperbolic sine of {expr}
+slice({expr}, {start} [, {end}])  String, List or Blob
+					slice of a String, List or Blob
 sort({list} [, {func} [, {dict}]])
 				List	sort {list}, using {func} to compare
 sound_clear()			none	stop playing all sounds
@@ -9862,6 +9870,18 @@ sinh({expr})						*sinh()*
 		{only available when compiled with the |+float| feature}
 
 
+slice({expr}, {start} [, {end}])			*slice()* 
+		Similar to using a |slice| "expr[start : end]", but "end" is
+		used exclusive.  And for a string the indexes are used as
+		character indexes instead of byte indexes, like in
+		|vim9script|.
+		When {end} is omitted the slice continues to the last item.
+		When {end} is -1 the last item is omitted.
+
+		Can also be used as a |method|: >
+			GetList()->slice(offset)
+
+
 sort({list} [, {func} [, {dict}]])			*sort()* *E702*
 		Sort the items in {list} in-place.  Returns {list}.
 

runtime/doc/usr_41.txt

@@ -619,6 +619,8 @@ String manipulation:					*string-functions*
 	submatch()		get a specific match in ":s" and substitute()
 	strpart()		get part of a string using byte index
 	strcharpart()		get part of a string using char index
+	slice()			take a slice of a string, using char index in
+				Vim9 script
 	strgetchar()		get character from a string using char index
 	expand()		expand special keywords
 	expandcmd()		expand a command like done for `:edit`
@@ -648,6 +650,7 @@ List manipulation:					*list-functions*
 	map()			change each List item
 	mapnew()		make a new List with changed items
 	reduce()		reduce a List to a value
+	slice()			take a slice of a List
 	sort()			sort a List
 	reverse()		reverse the order of a List
 	uniq()			remove copies of repeated adjacent items

src/eval.c

@@ -3877,8 +3877,9 @@ eval_index(
     if (evaluate)
     {
 	int res = eval_index_inner(rettv, range,
-		empty1 ? NULL : &var1, empty2 ? NULL : &var2,
+		empty1 ? NULL : &var1, empty2 ? NULL : &var2, FALSE,
 		key, keylen, verbose);
+
 	if (!empty1)
 	    clear_tv(&var1);
 	if (range)
@@ -3937,10 +3938,27 @@ check_can_index(typval_T *rettv, int evaluate, int verbose)
     return OK;
 }
 
+/*
+ * slice() function
+ */
+    void
+f_slice(typval_T *argvars, typval_T *rettv)
+{
+    if (check_can_index(argvars, TRUE, FALSE) == OK)
+    {
+	copy_tv(argvars, rettv);
+	eval_index_inner(rettv, TRUE, argvars + 1,
+		argvars[2].v_type == VAR_UNKNOWN ? NULL : argvars + 2,
+		TRUE, NULL, 0, FALSE);
+    }
+}
+
 /*
  * Apply index or range to "rettv".
  * "var1" is the first index, NULL for [:expr].
  * "var2" is the second index, NULL for [expr] and [expr: ]
+ * "exclusive" is TRUE for slice(): second index is exclusive, use character
+ * index for string.
  * Alternatively, "key" is not NULL, then key[keylen] is the dict index.
  */
     int
@@ -3949,11 +3967,12 @@ eval_index_inner(
 	int	    is_range,
 	typval_T    *var1,
 	typval_T    *var2,
+	int	    exclusive,
 	char_u	    *key,
 	int	    keylen,
 	int	    verbose)
 {
-    long	n1, n2 = 0;
+    varnumber_T	    n1, n2 = 0;
     long	    len;
 
     n1 = 0;
@@ -3968,10 +3987,10 @@ eval_index_inner(
 		emsg(_(e_cannot_slice_dictionary));
 	    return FAIL;
 	}
-	if (var2 == NULL)
+	if (var2 != NULL)
-	    n2 = -1;
-	else
 	    n2 = tv_get_number(var2);
+	else
+	    n2 = VARNUM_MAX;
     }
 
     switch (rettv->v_type)
@@ -3994,10 +4013,10 @@ eval_index_inner(
 		char_u	*s = tv_get_string(rettv);
 
 		len = (long)STRLEN(s);
-		if (in_vim9script())
+		if (in_vim9script() || exclusive)
 		{
 		    if (is_range)
-			s = string_slice(s, n1, n2);
+			s = string_slice(s, n1, n2, exclusive);
 		    else
 			s = char_from_string(s, n1);
 		}
@@ -4015,6 +4034,8 @@ eval_index_inner(
 			n2 = len + n2;
 		    else if (n2 >= len)
 			n2 = len;
+		    if (exclusive)
+			--n2;
 		    if (n1 >= len || n2 < 0 || n1 > n2)
 			s = NULL;
 		    else
@@ -4051,7 +4072,9 @@ eval_index_inner(
 		if (n2 < 0)
 		    n2 = len + n2;
 		else if (n2 >= len)
-		    n2 = len - 1;
+		    n2 = len - (exclusive ? 0 : 1);
+		if (exclusive)
+		    --n2;
 		if (n1 >= len || n2 < 0 || n1 > n2)
 		{
 		    clear_tv(rettv);
@@ -4103,9 +4126,9 @@ eval_index_inner(
 	    if (var1 == NULL)
 		n1 = 0;
 	    if (var2 == NULL)
-		n2 = -1;
+		n2 = VARNUM_MAX;
 	    if (list_slice_or_index(rettv->vval.v_list,
-				    is_range, n1, n2, rettv, verbose) == FAIL)
+			  is_range, n1, n2, exclusive, rettv, verbose) == FAIL)
 		return FAIL;
 	    break;
 

src/evalfunc.c

@@ -1500,6 +1500,8 @@ static funcentry_T global_functions[] =
 			ret_float,	    FLOAT_FUNC(f_sin)},
     {"sinh",		1, 1, FEARG_1,	    NULL,
 			ret_float,	    FLOAT_FUNC(f_sinh)},
+    {"slice",		2, 3, FEARG_1,	    NULL,
+			ret_first_arg,	    f_slice},
     {"sort",		1, 3, FEARG_1,	    NULL,
 			ret_first_arg,	    f_sort},
     {"sound_clear",	0, 0, 0,	    NULL,

src/list.c

@@ -905,14 +905,15 @@ list_slice(list_T *ol, long n1, long n2)
 list_slice_or_index(
 	    list_T	*list,
 	    int		range,
-	    long	n1_arg,
+	    varnumber_T	n1_arg,
-	    long	n2_arg,
+	    varnumber_T	n2_arg,
+	    int		exclusive,
 	    typval_T	*rettv,
 	    int		verbose)
 {
     long	len = list_len(list);
-    long	n1 = n1_arg;
+    varnumber_T	n1 = n1_arg;
-    long	n2 = n2_arg;
+    varnumber_T	n2 = n2_arg;
     typval_T	var1;
 
     if (n1 < 0)
@@ -936,7 +937,9 @@ list_slice_or_index(
 	if (n2 < 0)
 	    n2 = len + n2;
 	else if (n2 >= len)
-	    n2 = len - 1;
+	    n2 = len - (exclusive ? 0 : 1);
+	if (exclusive)
+	    --n2;
 	if (n2 < 0 || n2 + 1 < n1)
 	    n2 = -1;
 	l = list_slice(list, n1, n2);

src/proto/eval.pro

@@ -41,7 +41,8 @@ void eval_addblob(typval_T *tv1, typval_T *tv2);
 int eval_addlist(typval_T *tv1, typval_T *tv2);
 int eval_leader(char_u **arg, int vim9);
 int check_can_index(typval_T *rettv, int evaluate, int verbose);
-int eval_index_inner(typval_T *rettv, int is_range, typval_T *var1, typval_T *var2, char_u *key, int keylen, int verbose);
+void f_slice(typval_T *argvars, typval_T *rettv);
+int eval_index_inner(typval_T *rettv, int is_range, typval_T *var1, typval_T *var2, int exclusive, char_u *key, int keylen, int verbose);
 char_u *partial_name(partial_T *pt);
 void partial_unref(partial_T *pt);
 int get_copyID(void);
@@ -58,7 +59,7 @@ int string2float(char_u *text, float_T *value);
 int buf_byteidx_to_charidx(buf_T *buf, int lnum, int byteidx);
 int buf_charidx_to_byteidx(buf_T *buf, int lnum, int charidx);
 pos_T *var2fpos(typval_T *varp, int dollar_lnum, int *fnum, int charcol);
-int list2fpos(typval_T *arg, pos_T *posp, int *fnump, colnr_T *curswantp, int char_col);
+int list2fpos(typval_T *arg, pos_T *posp, int *fnump, colnr_T *curswantp, int charcol);
 int get_env_len(char_u **arg);
 int get_id_len(char_u **arg);
 int get_name_len(char_u **arg, char_u **alias, int evaluate, int verbose);

src/proto/list.pro

@@ -34,7 +34,7 @@ void f_flatten(typval_T *argvars, typval_T *rettv);
 int list_extend(list_T *l1, list_T *l2, listitem_T *bef);
 int list_concat(list_T *l1, list_T *l2, typval_T *tv);
 list_T *list_slice(list_T *ol, long n1, long n2);
-int list_slice_or_index(list_T *list, int range, long n1_arg, long n2_arg, typval_T *rettv, int verbose);
+int list_slice_or_index(list_T *list, int range, varnumber_T n1_arg, varnumber_T n2_arg, int exclusive, typval_T *rettv, int verbose);
 list_T *list_copy(list_T *orig, int deep, int copyID);
 void vimlist_remove(list_T *l, listitem_T *item, listitem_T *item2);
 char_u *list2string(typval_T *tv, int copyID, int restore_copyID);

src/proto/vim9execute.pro

@@ -2,7 +2,7 @@
 void to_string_error(vartype_T vartype);
 void funcstack_check_refcount(funcstack_T *funcstack);
 char_u *char_from_string(char_u *str, varnumber_T index);
-char_u *string_slice(char_u *str, varnumber_T first, varnumber_T last);
+char_u *string_slice(char_u *str, varnumber_T first, varnumber_T last, int exclusive);
 int fill_partial_and_closure(partial_T *pt, ufunc_T *ufunc, ectx_T *ectx);
 int call_def_function(ufunc_T *ufunc, int argc_arg, typval_T *argv, partial_T *partial, typval_T *rettv);
 void ex_disassemble(exarg_T *eap);

src/testdir/test_vim9_builtin.vim

@@ -741,6 +741,29 @@ def Test_setreg()
   getreginfo('a')->assert_equal(reginfo)
 enddef 
 
+def Test_slice()
+  assert_equal('12345', slice('012345', 1))
+  assert_equal('123', slice('012345', 1, 4))
+  assert_equal('1234', slice('012345', 1, -1))
+  assert_equal('1', slice('012345', 1, -4))
+  assert_equal('', slice('012345', 1, -5))
+  assert_equal('', slice('012345', 1, -6))
+
+  assert_equal([1, 2, 3, 4, 5], slice(range(6), 1))
+  assert_equal([1, 2, 3], slice(range(6), 1, 4))
+  assert_equal([1, 2, 3, 4], slice(range(6), 1, -1))
+  assert_equal([1], slice(range(6), 1, -4))
+  assert_equal([], slice(range(6), 1, -5))
+  assert_equal([], slice(range(6), 1, -6))
+
+  assert_equal(0z1122334455, slice(0z001122334455, 1))
+  assert_equal(0z112233, slice(0z001122334455, 1, 4))
+  assert_equal(0z11223344, slice(0z001122334455, 1, -1))
+  assert_equal(0z11, slice(0z001122334455, 1, -4))
+  assert_equal(0z, slice(0z001122334455, 1, -5))
+  assert_equal(0z, slice(0z001122334455, 1, -6))
+enddef
+
 def Test_spellsuggest()
   if !has('spell')
     MissingFeature 'spell'

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2344,
 /**/
     2343,
 /**/

src/vim9execute.c

@@ -965,10 +965,11 @@ char_idx2byte(char_u *str, size_t str_len, varnumber_T idx)
 
 /*
  * Return the slice "str[first:last]" using character indexes.
+ * "exclusive" is TRUE for slice().
  * Return NULL when the result is empty.
  */
     char_u *
-string_slice(char_u *str, varnumber_T first, varnumber_T last)
+string_slice(char_u *str, varnumber_T first, varnumber_T last, int exclusive)
 {
     long	start_byte, end_byte;
     size_t	slen;
@@ -979,12 +980,12 @@ string_slice(char_u *str, varnumber_T first, varnumber_T last)
     start_byte = char_idx2byte(str, slen, first);
     if (start_byte < 0)
 	start_byte = 0; // first index very negative: use zero
-    if (last == -1)
+    if ((last == -1 && !exclusive) || last == VARNUM_MAX)
 	end_byte = (long)slen;
     else
     {
 	end_byte = char_idx2byte(str, slen, last);
-	if (end_byte >= 0 && end_byte < (long)slen)
+	if (!exclusive && end_byte >= 0 && end_byte < (long)slen)
 	    // end index is inclusive
 	    end_byte += MB_CPTR2LEN(str + end_byte);
     }
@@ -2992,7 +2993,7 @@ call_def_function(
 		    tv = STACK_TV_BOT(-1);
 		    if (is_slice)
 			// Slice: Select the characters from the string
-			res = string_slice(tv->vval.v_string, n1, n2);
+			res = string_slice(tv->vval.v_string, n1, n2, FALSE);
 		    else
 			// Index: The resulting variable is a string of a
 			// single character.  If the index is too big or
@@ -3030,8 +3031,8 @@ call_def_function(
 		    ectx.ec_stack.ga_len -= is_slice ? 2 : 1;
 		    tv = STACK_TV_BOT(-1);
 		    SOURCING_LNUM = iptr->isn_lnum;
-		    if (list_slice_or_index(list, is_slice, n1, n2, tv, TRUE)
+		    if (list_slice_or_index(list, is_slice, n1, n2, FALSE,
-								       == FAIL)
+							     tv, TRUE) == FAIL)
 			goto on_error;
 		}
 		break;
@@ -3052,8 +3053,8 @@ call_def_function(
 			goto on_error;
 		    var1 = is_slice ? STACK_TV_BOT(-2) : STACK_TV_BOT(-1);
 		    var2 = is_slice ? STACK_TV_BOT(-1) : NULL;
-		    res = eval_index_inner(tv, is_slice,
+		    res = eval_index_inner(tv, is_slice, var1, var2,
-						   var1, var2, NULL, -1, TRUE);
+							FALSE, NULL, -1, TRUE);
 		    clear_tv(var1);
 		    if (is_slice)
 			clear_tv(var2);