Re: match-string debugging problem

[Alan Wehmann]

Stephen Berman <Stephen.Berman@gmx.net> writes:

> There seems to be something about match-string that I don't
> understand.  Here is an example of the kind of code I'm working with:
>
> (defvar mystring1 "+++++ ")
> (defvar mystring2 " ~~~~~")
> (defun mystring-list ()
>   (interactive)
>   (with-current-buffer (get-buffer-create "*test*")
>     (switch-to-buffer "*test*")
>     (dotimes (num 5)
>       (insert mystring1 "test" (int-to-string (1+ num)) mystring2 "\n"))
>     (goto-char (point-min))
>     (let ((mystring-list ()))
>       (while (re-search-forward
>             (concat "^" (regexp-quote mystring1) "\\(.+\\)"
>                     (regexp-quote mystring2) "$")
>             (point-max) t)
>       (setq mystring-list (append (list (match-string 1)) mystring-list)))
>       (insert "\n")
>       (setq mystring-list (reverse mystring-list))
>       (dolist (elt mystring-list)
>       (insert elt " ")))))
>
> After evalling this code and typing `M-x mystring-list', buffer *test*
> consists of these lines:
>
> +++++ test1 ~~~~~
> +++++ test2 ~~~~~
> +++++ test3 ~~~~~
> +++++ test4 ~~~~~
> +++++ test5 ~~~~~
> test1 test2 test3 test4 test5 
>
> The last line indicates that match-string correctly matches the
> strings that build mystring-list.  But when I step through the code
> with edebug, match-string always returns nil and a wrong-type-argument
> error is raised at the insert (since nil is not char-or-string-p).
> (Edebug isn't the problem: evalling first the regexp search code in
> *test* and then (match-string 1) also returns nil.)  Because of this
> I'm having a hard time debugging other code that uses match-string.
> Can someone explain what's going on?
>
> Steve Berman
>
>
>
I tried your example, with 

GNU Emacs 21.2.2 (sparc-sun-solaris2.8, X toolkit) of 2005-02-10 on
gax

and also with

XEmacs 21.4 (patch 15) "Security Through Obscurity" [Lucid]
(sparc-sun-solaris2.8, Mule) of Fri Feb 11 2005 on gax

When I put a breakpoint in Edebug after

(match-string 1)

I get the strings I expect to see.  Also, a breakpoint after 'elt' in

        (insert elt " ")

behaves as I would expect & not as you describe.
-- 
Alan Wehmann
wehmann(removespam)@fnal.gov