Re: query-replace-regexp: Can't use \0 in TO-STRING

[zhanghj <netjunegg@gmail.com>]

Tino Calancha <tino.calancha@gmail.com> writes:

>> Why not \0? I think \0 is more intuitive and also used in vim.
> I agree is more intuitive, and it works in `replace-match', or instance:
> (mapcar
>  (lambda (group)
>    (let ((str "foo123"))
>      (when (string-match "[a-z]+\\([1-9]+\\)" str)
>        (replace-match "bar" nil nil str group))))
>  (list 0 1))
> => ("bar" "foobar")
>
> Are you willing to write a patch to implement it?

The following patch works on my machine for regexp replacing. But I
don't known if \0 should be supported in other places such as
sort-regexp-fields, occur.

diff --git a/lisp/subr.el b/lisp/subr.el
index 02e7993..c182128 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -3634,7 +3634,7 @@ match-string-no-properties
 (defun match-substitute-replacement (replacement
 				     &optional fixedcase literal string subexp)
   "Return REPLACEMENT as it will be inserted by `replace-match'.
-In other words, all back-references in the form `\\&' and `\\N'
+In other words, all back-references in the form `\\&', `\\0' and `\\N'
 are substituted with actual strings matched by the last search.
 Optional FIXEDCASE, LITERAL, STRING and SUBEXP have the same
 meaning as for `replace-match'."
diff --git a/src/search.c b/src/search.c
index 1223cbf..86255f0 100644
--- a/src/search.c
+++ b/src/search.c
@@ -2339,7 +2339,7 @@ in the replaced text, capitalize each word in NEWTEXT.
 
 If optional third arg LITERAL is non-nil, insert NEWTEXT literally.
 Otherwise treat `\\' as special:
-  `\\&' in NEWTEXT means substitute original matched text.
+  `\\&' or `\\0' in NEWTEXT means substitute original matched text.
   `\\N' means substitute what matched the Nth `\\(...\\)'.
        If Nth parens didn't match, substitute nothing.
   `\\\\' means insert one `\\'.
@@ -2523,7 +2523,7 @@ since only regular expressions have distinguished subexpressions.  */)
 		{
 		  FETCH_STRING_CHAR_ADVANCE (c, newtext, pos, pos_byte);
 
-		  if (c == '&')
+		  if (c == '&' || c == '0')
 		    {
 		      substart = search_regs.start[sub];
 		      subend = search_regs.end[sub];
@@ -2668,7 +2668,7 @@ since only regular expressions have distinguished subexpressions.  */)
 		    MAKE_CHAR_MULTIBYTE (c);
 		}
 
-	      if (c == '&')
+	      if (c == '&' || c == '0')
 		idx = sub;
 	      else if (c >= '1' && c <= '9' && c - '0' < search_regs.num_regs)
 		{