45 lines
1016 B
Scheme
45 lines
1016 B
Scheme
(define (nth li pos)
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(cond
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((null? li) #f)
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((= pos 0) (car li))
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(#t (nth (cdr li) (- pos 1)))))
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(define (rangeinc b e)
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(cond
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((> b e) '())
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(#t (cons b (rangeinc (+ 1 b) e)))))
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(define (less-than l n)
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(cond
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((null? l) #t)
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((<= n 0) #f)
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(#t (less-than (cdr l) (- n 1)))))
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(define (beginning l n)
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(cond
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((null? l) '())
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((<= n 0) '())
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(#t (cons (car l) (beginning (cdr l) (- n 1))))))
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(define (unit v) v)
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(define (aget key alist) (cdr (assoc key alist)))
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(define (aset key val alist)
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(cond
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((null? alist) `((,key . ,val)))
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((eqv? (caar alist) key) (cons `(,key . ,val) (cdr alist))) ; found and updated
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(#t (cons (car alist) (aset key val (cdr alist)))) ; continue to seek
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))
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(define (dedup l p c)
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(cond
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((null? l) `(((str . ,p) (ctr . ,c))))
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((string=? p (car l)) (dedup (cdr l) p (+ c 1)))
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(#t (cons `((str . ,p) (ctr . ,c)) (dedup (cdr l) (car l) 1)))
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))
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(define (dedup<=? d1 d2)
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(<= (aget 'ctr d1) (aget 'ctr d2)))
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