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From: Kaz Kylheku <643-408-1753@kylheku.com>
Newsgroups: comp.lang.lisp
Subject: Re: Multivalue tail recursion?
Date: Thu, 19 Jun 2025 22:40:27 -0000 (UTC)
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On 2025-06-19, B. Pym <Nobody447095@here-nor-there.org> wrote:
>> 
>>  (loop for x in '(3 5 7)
>>        for y in '(2 5 8)
>>        when (= x y)
>>          collect (cons x y))
>
>
> What if there were more than two lists?
> This will handle any number of lists:
>
> Scheme:
>
> (filter-map
>   (lambda xs (and (apply = xs) xs))

What's wrong with (if (apply = xs) xs)?

>   '(0   3 5   7 9)
>   '(0   2 5.0 8 9.0)
>   '(2   4 5   8 9))
>
> ((5 5.0 5) (9 9.0 9))

This is nicer:

1> (mappend [iff = [chain list list]]
           '(0   3 5   7 9)
           '(0   2 5.0 8 9.0)
           '(2   4 5   8 9))
((5 5.0 5) (9 9.0 9))


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