how to search and replace in nested expressions

how to search and replace in nested expressions

[JAMES FUNDERBURK]

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.



Thanks for any suggestions.

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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