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35 lines
1 KiB
Scheme
35 lines
1 KiB
Scheme
;; constructors.scm -- list construction utilities
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;; Copyright (c) 2009-2012 Alex Shinn. All rights reserved.
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;; BSD-style license: http://synthcode.com/license.txt
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(define (xcons a b) (cons b a))
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(define (cons* x . args)
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(let lp ((rev '()) (x x) (ls args))
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(if (null? ls)
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(append-reverse rev x)
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(lp (cons x rev) (car ls) (cdr ls)))))
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(define (make-list n . o)
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(let ((default (if (pair? o) (car o))))
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(let lp ((n n) (res '()))
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(if (<= n 0) res (lp (- n 1) (cons default res))))))
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(define (list-tabulate n proc)
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(let lp ((n (- n 1)) (res '()))
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(if (< n 0) res (lp (- n 1) (cons (proc n) res)))))
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(define (list-copy ls) (reverse! (reverse ls)))
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(define (circular-list x . args)
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(let ((res (cons x args)))
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(set-cdr! (last-pair res) res)
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res))
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(define (iota count . o)
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(let ((start (if (pair? o) (car o) 0))
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(step (if (and (pair? o) (pair? (cdr o))) (cadr o) 1)))
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(let lp ((i count) (res '()))
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(if (<= i 0)
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res
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(lp (- i 1) (cons (+ start (* (- i 1) step)) res))))))
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