patch 8.2.1461: Vim9: string indexes are counted in bytes
Problem: Vim9: string indexes are counted in bytes.
Solution: Use character indexes. (closes #6574)
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index c579ed2..0203788 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -1131,19 +1131,25 @@
expr8[expr1] item of String or |List| *expr-[]* *E111*
*E909* *subscript*
+In legacy Vim script:
If expr8 is a Number or String this results in a String that contains the
-expr1'th single byte from expr8. expr8 is used as a String, expr1 as a
-Number. This doesn't recognize multi-byte encodings, see `byteidx()` for
-an alternative, or use `split()` to turn the string into a list of characters.
-
-Index zero gives the first byte. This is like it works in C. Careful:
-text column numbers start with one! Example, to get the byte under the
-cursor: >
+expr1'th single byte from expr8. expr8 is used as a String (a number is
+automatically converted to a String), expr1 as a Number. This doesn't
+recognize multi-byte encodings, see `byteidx()` for an alternative, or use
+`split()` to turn the string into a list of characters. Example, to get the
+byte under the cursor: >
:let c = getline(".")[col(".") - 1]
+In Vim9 script:
+If expr8 is a String this results in a String that contains the expr1'th
+single character from expr8. To use byte indexes use |strpart()|.
+
+Index zero gives the first byte or character. Careful: text column numbers
+start with one!
+
If the length of the String is less than the index, the result is an empty
String. A negative index always results in an empty string (reason: backward
-compatibility). Use [-1:] to get the last byte.
+compatibility). Use [-1:] to get the last byte or character.
If expr8 is a |List| then it results the item at index expr1. See |list-index|
for possible index values. If the index is out of range this results in an
@@ -1157,10 +1163,16 @@
expr8[expr1a : expr1b] substring or sublist *expr-[:]*
-If expr8 is a Number or String this results in the substring with the bytes
-from expr1a to and including expr1b. expr8 is used as a String, expr1a and
-expr1b are used as a Number. This doesn't recognize multi-byte encodings, see
-|byteidx()| for computing the indexes.
+If expr8 is a String this results in the substring with the bytes from expr1a
+to and including expr1b. expr8 is used as a String, expr1a and expr1b are
+used as a Number.
+
+In legacy Vim script the indexes are byte indexes. This doesn't recognize
+multi-byte encodings, see |byteidx()| for computing the indexes. If expr8 is
+a Number it is first converted to a String.
+
+In Vim9 script the indexes are character indexes. To use byte indexes use
+|strpart()|.
If expr1a is omitted zero is used. If expr1b is omitted the length of the
string minus one is used.