Re: Evaluation of macro arguments

["Pascal J. Bourguignon" <pjb@informatimago.com>]

Marcin Borkowski <mbork@mbork.pl> writes:

> Hi all,
>
> continuing my quest to grok macro argument evaluation issues, I'd like
> (again) to make sure that I get it correctly.  So I have this simple
> macro generating a list of consecutive numbers (which is not without
> problems - I am aware of those, namely (i) it uses hard-coded symbols
> instead of generating them on the fly, and (ii) it has no error
> checking):
>
> (defmacro range (from dir to)
>   `(let ((delta (cond ((eq ',dir 'upto) 1)
>                       ((eq ',dir 'downto) -1)))
>          (i ,from)
>          (list nil))
>      (while (not (= i ,to))
>        (push i list)
>        (setq i (+ i delta)))
>      (nreverse list)))

(let ((i 0))
   (list (range  i 'upto (incf i 10))  ; bam!
         i))

I hope you may debug it well.


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