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RE: I'd like to marry while and mapcar...

From: Doug Lewan
Subject: RE: I'd like to marry while and mapcar...
Date: Fri, 6 Feb 2015 13:44:29 +0000

There are already a few small programming paradigms for such things.

(dolist (VAR LIST [RESULT]) BODY...) might do the right kind of thing for you, 
but it never feels lisp-ish to me. And on a long list you might not get the 
efficiency you expect.

(while (and magic-condition the-list) ... (setq the-list (cdr the-list)) seems 

(throw) and (catch) provide another style:
(catch 'foo
  (mapcar (lambda (e)
             (if (not (magic-test e))
                (throw 'foo t)))))

I hope this helps.

Douglas Lewan
Shubert Ticketing
(201) 489-8600 ext 224 or ext 4335

The human brain is the most complex thing known to man, according to the human 

> -----Original Message-----
> From: address@hidden
> [mailto:address@hidden On
> Behalf Of Marcin Borkowski
> Sent: Friday, 2015 February 06 07:57
> To: Help Gnu Emacs mailing list
> Subject: I'd like to marry while and mapcar...
> Hello Emacsers and Elispers!
> What I'd need is kind of a marriage of while and mapcar: I'd like to
> run
> some function until it returns nil and make a list of all results it
> gives back until then.
> Mu use case is that I'm getting some info from a LaTeX file.  For
> instance, assume that I want to make a list of all files \include'd by
> a LaTeX document.  I've written a function `get-TeX-macro-arguments'
> which finds the next occurence of a given TeX command, moves point past
> it and returns its arguments; if it does not find any such occurrence,
> it returns nil.  So I can say something like this:
> (let (current-include (list-of-includes ()))
>   (while (setq current-include (get-TeX-macro-arguments "include"))
>     (setq list-of-includes (append list-of-includes current-include)))
>   list-of-includes)
> This, however, looks a bit, let's say, Fortran-ish;-); I'm after a more
> Lispy way.  (Of course, one step would be to use anaphoric while, but
> that doesn't help my main problem of ditching list-of-includes.)
> Yes, I know, I have too much time on my hands, and I bother about
> style.
> But I'm also curious whether there is any "standard" way, or whether
> I should indeed wrap something like the above code in a macro, or
> something.  (Or maybe just don't care...)
> TIA,
> --
> Marcin Borkowski               This email was proudly sent
>                from my Emacs.

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