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devel / comp.lang.lisp / .Re: cloning elements in a list

.Re: cloning elements in a list

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https://www.rocksolidbbs.com/devel/article-flat.php?id=16916&group=comp.lang.lisp#16916

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From: No_spamming@noWhere_7073.org (Robert L.)
Newsgroups: comp.lang.lisp
Subject: .Re: cloning elements in a list
Date: Tue, 22 Feb 2022 23:53:07 -0000 (UTC)
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by: Robert L. - Tue, 22 Feb 2022 23:53 UTC

> > How to write a lisp function which clones the top-level elements of a list
> L
> > (first arguement) n ( second argument) times. for eg. (clone 'A B C) 4 )
> > produces ( AAAABBBBCCCC)
>
> To rewrite your question to what I *think* you mean:
> (clone '(A B C) 4 )
> => (A A A A B B B B C C C C)
>
> try this:
> CL-USER 143 > (defun stretch (list factor)
> (loop for elt in list
> nconc (make-list factor :initial-element elt)))
> STRETCH
>
> CL-USER 144 > (stretch '(a b c) 4)
> (A A A A B B B B C C C C)

Scheme:

(define (stretch lst factor . xs)
(if (zero? factor)
(apply append-map list xs)
(apply stretch lst (- factor 1) (cons lst xs))))

(stretch '(a b c) 4)
===>
(a a a a b b b b c c c c)

Subject	Author
.Re: cloning elements in a list	Robert L.