[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Evaluation of macro arguments
From: |
Marcin Borkowski |
Subject: |
Re: Evaluation of macro arguments |
Date: |
Tue, 05 Jan 2016 21:30:35 +0100 |
User-agent: |
mu4e 0.9.13; emacs 25.1.50.1 |
On 2016-01-05, at 20:39, Marcin Borkowski <mbork@mbork.pl> wrote:
> On 2016-01-05, at 20:22, Pascal J. Bourguignon <pjb@informatimago.com> wrote:
>
>> 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.
>
> That's unfair, Pascal; I wrote that I'm aware of this, I know how to
> make it work, and wasn't asking about it.
OK, technically you win, since I didn't notice that I evaluated `to'
multiple times. Still, this was not what I was asking about - though
thank you for pointing that out to me. It would be rather embarassing
if I missed it.
Best,
--
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Faculty of Mathematics and Computer Science
Adam Mickiewicz University
Re: Evaluation of macro arguments, Pascal J. Bourguignon, 2016/01/05