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 (cddadr x) (cdr (cdr (car (cdr x)))))
(define (cdddar x) (cdr (cdr (cdr (car x))))) (define (cdddar x) (cdr (cdr (cdr (car x)))))
(define (cddddr x) (cdr (cdr (cdr (cdr 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)))