Re: using lisp in replacement string

[Emanuel Berg]

Guido Van Hoecke <guivho@gmail.com> writes:

> So I have a temp buffer with following content
> |2+6*21|
> |3*15|
> |7-3|
> and I want to replace the formulas between the '|'
> characters by the result of passing them to
> calc-eval

Yes, you can do that! I did that once with a file like
this:

   normal                         bright
   bk  r   g   y  bl   m   c   w  bk    r   g   y  bl   m   c   w
r  0 233  50 170 100 200   0 150  110 255   0 220 133 255   0 190
g  0   0 150 170 100   0 170 150  110  33 190 220 133   0 190 190
b  0   0  50   0 200 200 170 150  110  33   0   0 255 255 190 190

I thought it could be cool to, for example, add 10% to
each - the span is (as you see) 0 to 255, so +10% from
150 would be ... 177?

Anyway, I got rid of that code because it was much
easier and more powerful to just tweak it by hand,
digit by digit. Still, it is the exact situation as
yours - replace a value by another value, that is a
function of the first value - or, replace x by f(x) -
so I can tell you how I did it. (Let this be a lesson
to naive Elispers - including those who verbalize the
lesson - always keep your code, even that which you
don't use...)

Now: check out this, from the help of
`replace-regexp'.

(while (re-search-forward REGEXP nil t)
  (replace-match TO-STRING nil nil))

So instead of the `replace-match' stuff above, you
write a function that examines `match-beginning',
`match-end', and `match-string', and then use that as
input to your Elisp, to produce the on-the-fly
TO-STRING (in the phrasing of the above Elisp).

Good luck!

(And when you get it to work, post it here :))

-- 
underground experts united