RetroBBS - comp.lang.lisp - When to use apply

When to use apply

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From: No_spamming@noWhere_7073.org (Robert L.)
Newsgroups: comp.lang.lisp
Subject: When to use apply
Date: Fri, 11 Feb 2022 09:06:10 -0000 (UTC)
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by: Robert L. - Fri, 11 Feb 2022 09:06 UTC

> Of course, after going through all of that you then see why loop is so
> handy:
>
> CL-USER> (defun nth-elements (n &rest lists)
> (loop for item in lists collect (nth n item)))
>
> NTH-ELEMENTS
> CL-USER> (nth-elements 3 '(10 20 hello x world) '(-1 -2 -3 y) '(z0 z1 z2 z))
>
> (X Y Z)

Instead of CL, let's use a Lisp.

Gauche Scheme:

(define (nth-elements n . seqs)
(map (cut list-ref <> n 'too-short) seqs))

(nth-elements 3
'(foo bar)
'(10 20 hello x world)
'(-1 -2 -3 y)
'(z0 z1 z2 z))

===>
(too-short x y z)

Phasers locked on target, Captain.

devel / comp.lang.lisp / When to use apply

devel / comp.lang.lisp / When to use apply