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From: Kaz Kylheku <643-408-1753@kylheku.com>
Newsgroups: comp.lang.lisp
Subject: Re: CAR/CDR vs FIRST/REST
Date: Fri, 13 Sep 2024 00:47:57 -0000 (UTC)
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On 2024-09-12, B. Pym <Nobody447095@here-nor-there.org> wrote:
> Barry Margolin wrote:
>
>> >       (mapcan #'(lambda (x) (and (numberp x) (list x))) list)
>> 
>> >       (loop for x in list
>> >               when (numberp x) collect x)
>> 
>> I agree with this example.  Once I learned LOOP I never used the
>> above idiom again.

>
> (filter number? '(a b c 1 2 3))
> ===>
> (1 2 3)

Also, once you realize that "remove-if-not" is "keep-if":

  (remove-if-not #'numberp list)

then you also will not use the poor "idiom":

  (mapcan #'(lambda (x) (and (numberp x) (list x))) list)

Not to mention that once you learn that (lambda ...) is
a macro which writes #'(lambda ...) for you, you will tend
not to use the latter again.

-- 
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