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comp / comp.lang.lisp / Re: CAR/CDR vs FIRST/REST

SubjectAuthor
* Re: CAR/CDR vs FIRST/RESTB. Pym
`- Re: CAR/CDR vs FIRST/RESTKaz Kylheku

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Subject: Re: CAR/CDR vs FIRST/REST
From: B. Pym
Newsgroups: comp.lang.lisp
Organization: A noiseless patient Spider
Date: Tue, 2 Jul 2024 21:33 UTC
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From: No_spamming@noWhere_7073.org (B. Pym)
Newsgroups: comp.lang.lisp
Subject: Re: CAR/CDR vs FIRST/REST
Date: Tue, 2 Jul 2024 21:33:23 -0000 (UTC)
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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)

Subject: Re: CAR/CDR vs FIRST/REST
From: Kaz Kylheku
Newsgroups: comp.lang.lisp
Organization: A noiseless patient Spider
Date: Tue, 2 Jul 2024 22:58 UTC
References: 1
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From: 643-408-1753@kylheku.com (Kaz Kylheku)
Newsgroups: comp.lang.lisp
Subject: Re: CAR/CDR vs FIRST/REST
Date: Tue, 2 Jul 2024 22:58:00 -0000 (UTC)
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On 2024-07-02, B. Pym <No_spamming@noWhere_7073.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)

In Common Lisp, filter has a funny name: remove-if-not.

(remove-if-not #'numberp '(a b c 1 2 3))
-->
(1 2 3)

Likely because of the funny name, the function is marked deprecated,
which is silly.

--
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal
Mastodon: @Kazinator@mstdn.ca

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