Re: Basic questions about elisp

[tomas]

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On Thu, Nov 05, 2009 at 03:13:32AM -0800, Francis Moreau wrote:
> Hello,
> 
> I'm trying to learn elisp and have a couple of basic questions.
> 
> I'm iterating over a list using dotimes, but in the body of dotimes,
> the list can mutate. For example I have:
> 
>   (dolist (elt lst)
>     ;; some codes
>     (nconc lst '(2)))
> 
> This adds/appends a new element to 'lst' list. It looks like 'dotimes'
> doesn't like it.
> 
> So I eventually wrote it like this
> 
>     (setq i 0)
>     (while (< i (length lst))
>           ;; some codes
>           (x-nconc lst '(2))))
>       (setq i (1+ i)))
> 
> which is a bit ugly, is there another way to do that ?

What about:

  (let ((l lst))
    (while l
      (do-something-with (car l))
      (setq l (cdr l))))

This should be fine as long as you only append to lst. Dragons might
emerge whenever you do more drastic things to it ;-)

(and you would have to re-think things when Emacs Lisp becomes
multi-threaded. It might work then and it might not).

Regards
- -- tomás

> And finally, is it the good place to ask such questions about elisp ?

I'd think so, yes

Regards
- -- tomás
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