Re: how to search and replace in nested expressions

[Pascal Bourguignon]

"JAMES FUNDERBURK" <funderburk1@verizon.net> writes:

> Is there a way to search and replace in nested expressions?
>   The particular form of my nested expressions is
>      form[x,y,...z]  where each 'argument' may be either
>     a word (simple character string) or else
>     another nested expression.  Note that the arguments are
>     separated by commas, but there may be only one argument.
>     For example, it might be desired to change expressions of the form
>        simple[x,y] to simple[y,x]  in such a way that
>        simple[apple[u],pear[v,w]] is changed to
>        simple[pear[v,w],apple[u]].
>    I am familiar with Emacs-Lisp, so am looking for a function to do
>    such changes on a buffer.  I have used the regular expression search  and 
> replace functions quite a bit, but don't see how to apply them in this 
> situation.

Regular expressions are not powerfull enough to handle nested
expressions.  You need a parser.  That's why lisp (lack of) syntax is
best: you only need one simple parser to parse any language and any
data.

To change:
(simple (apple u) (pear v w))
into:
(simple (pear v w) (apple u))

I only need to type:

(replace-sexps (buffer-file-name (current-buffer))
               (lambda (sexp) (if (and (consp sexp)
                                  (eq 'simple (first sexp))
                                  (= 3 (length sexp)))
                           `(simple ,(third sexp) ,(second sexp))
                           sexp)) :deeply t)


http://www.informatimago.com/develop/emacs
cvs -z3 -d 
:pserver:anonymous@cvs.informatimago.com:/usr/local/cvs/public/chrooted-cvs/cvs 
co emacs
(see pjb-sources.el)


-- 
__Pascal Bourguignon__                     http://www.informatimago.com/

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