Re: query-replace-interactive not documented

[David Kastrup <dak@gnu.org>]

Juri Linkov <juri@jurta.org> writes:

> David Kastrup <dak@gnu.org> writes:
> > storm@cua.dk (Kim F. Storm) writes:
> >> Richard Stallman <rms@gnu.org> writes:
> >> > That seems like an interesting idea.
> >> 
> >> I would prefer a syntax which can be parsed with `read', which
> >> includes the second example above, but not the first one.
> >
> > Well, this was of course just a wild proposal without any serious
> > thought behind the involved details.  One should probably take a look
> > at eshell syntax maybe for getting some suggestions for a somewhat
> > consistent syntax, and one would need to think about a way that makes
> > it possible to end the expression in question without adding
> > unnecessary spaces or so to the match.
> 
> I like this idea.  To avoid problems with `read' and to end the expression
> explicitly I suggest to always place the expression in parenthesis.
> To use a single variable inside a replacement string, one can use
> a no-op function like `+':
> 
>     \\footnote{\\label{fn:\!(+ replace-count)}

If there are always to be parens around, then there would be no need for
!.  One could just write

\\footnote{\\label{fn:\(+ replace-count\)}

I don't see a good way around having to backslash the closing paren:
if one doesn't, paren matching goes awry.

> > And of course, this sort of stuff should not be done by
> > replace-match or similar functions but just by the interactive
> > function, to avoid opening security concerns when Emacs is used as
> > a match-and-replace engine (where people don't expect it to
> > execute arbitrary code).
> 
> Doing it only in the interactive function instead of `replace-match'
> seems right.  This is needed only to save keystrokes for users.
> Since `replace-match' is not a command, when the programmer writes a
> loop with `re-search-forward' and `replace-match', he can construct
> a replacement string explicitly with appropriate functions.
> 
> Anyway, below is a quick implementation of such a feature.  I tried it
> a bit and I like it.  What I don't like yet is the choice of a special
> meta symbol `\!'.  Usually this symbol is associated with the error code.
> Perhaps, a better symbol would be \( itself like in:
> 
>     \\footnote{\\label{fn:\(+ replace-count)}
> 
> but this has another problem: the open parenthesis is escaped
> and Emacs commands don't match it with the close parenthesis.

Oh shucks.  That's what I get from replying before reading to the end.
Anyway, since it appears that we can hardly avoid using non-escaped
parens if we want to make use of the Lisp reader as well as paren
matching, one might as well use the original proposal allowing a
variable name directly.

How about using \'?  After all, we have an unevaled expression
following.

That would allow either

\\footnote{\\label{fn:\'(+ replace-count)}

or

\\footnote{\\label{fn:\'replace-count }}

Well, the latter has a spurious space.  Bother.

> Index: replace.el
> ===================================================================
> RCS file: /cvsroot/emacs/emacs/lisp/replace.el,v
> retrieving revision 1.172
> diff -c -r1.172 replace.el
> *** replace.el	10 Jun 2004 04:21:14 -0000	1.172
> --- replace.el	15 Jun 2004 14:56:15 -0000
> ***************
> *** 174,180 ****
>   	   (if (and transient-mark-mode mark-active)
>   	       (region-end)))))
>   
> !   (perform-replace regexp to-string t t delimited nil nil start end))
>   (define-key esc-map [?\C-%] 'query-replace-regexp)
>   
>   (defun query-replace-regexp-eval (regexp to-expr &optional delimited start end)
> --- 183,200 ----
>   	   (if (and transient-mark-mode mark-active)
>   	       (region-end)))))
>   
> !   (if (string-match "!\(" to-string)
> !       (let (res)
> !         (while (string-match "!\(" to-string)
> !           (setq res (cons (substring to-string 0 (1- (match-beginning 0))) res)
> !                 to-string (substring to-string (1- (match-end 0))))
> !           (let ((r (read-from-string to-string)))
> !             (setq res (cons `(format "%s" ,(car r)) res)
> !                   to-string (substring to-string (cdr r)))))
> !         (perform-replace regexp `(replace-eval-replacement
> !                                   concat ,@(nreverse (cons to-string res)))
> !                          t 'literal delimited nil nil start end))
> !     (perform-replace regexp to-string t t delimited nil nil start end)))
>   (define-key esc-map [?\C-%] 'query-replace-regexp)
>   
>   (defun query-replace-regexp-eval (regexp to-expr &optional delimited start end)

First you are matching against !( not against \!( or similar.  Then
you are not replacing any \1 \2 or similar sequences as far as I can
see.  It will probably not be easy to do this right: have the \(
replacement not being interpreted afterwards, but the non-evalled
ones still being interpreted.  Probably one needs to explicitly
double any \ returned from the evaluation, and then call
perform-replace with "t" instead of 'literal.

Something like that.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum