Re: Multivalue tail recursion?

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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