causa-arcana-misc/lesson-lisp
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funcs "list-tail", "list-ref"

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This commit is contained in:
Alex Kotov 2023-05-06 01:40:16 +04:00
parent 8482bd2dae
commit 9eca3ac0b9
Signed by: kotovalexarian
GPG key ID: 553C0EBBEB5D5F08
1 changed files with 7 additions and 0 deletions
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7
lib/lists.scm
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@ -28,3 +28,10 @@
(define (cddadr x) (cdr (cdr (car (cdr x)))))
(define (cdddar x) (cdr (cdr (cdr (car x)))))
(define (cddddr x) (cdr (cdr (cdr (cdr x)))))
(define (list-tail x k)
(if (zero? k)
x
(list-tail (cdr x) (- k 1))))
(define (list-ref x k) (car (list-tail x k)))