83 lines
1.3 KiB
Racket
83 lines
1.3 KiB
Racket
#lang racket
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(define (itlist f lst b)
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(if (null? lst)
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b
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(f (car lst) (itlist f (list-tail lst 1) b))))
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(define (sum lst)
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(itlist + lst 0))
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(define (prod lst)
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(itlist * lst 1))
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(define (mid p)
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(lambda (x s)
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(if (p x)
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(cons x s)
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s)))
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(define (filter p lst)
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(itlist (mid p) lst '()))
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(define (andt l b)
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(and l b))
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(define (ort l b)
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(or l b))
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(define (forall p lst)
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(define a true)
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(itlist andt (map p lst) a))
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(define (exists p lst)
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(define a false)
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(itlist ort (map p lst) a))
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(define (tem l b)
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(+ b 1))
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(define (length lst)
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(itlist tem lst 0))
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(define (append l m)
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(itlist cons l m))
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(define (const f)
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(lambda (x y) (cons (f x) y)))
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(define (map f l)
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(define s '())
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(define con (const f))
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(itlist con l s))
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(define (mem x lst)
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(exists (lambda (y) (= y x)) lst))
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(define (insert x lst)
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(if (mem x lst)
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lst
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(cons x lst)))
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(define (union l1 l2)
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(itlist insert l1 l2))
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(define (setify lst)
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(union lst '()))
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(define (Union lst)
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(itlist union lst '()))
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(define (notc l2)
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(lambda (x) (mem x l2)))
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(define (nonotc l2)
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(lambda (x) (not (mem x l2))))
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(define (intersect l1 l2)
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(filter (notc l2) l1))
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(define (subtract l1 l2)
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(filter (nonotc l2) l1))
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(define (subset l1 l2)
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(forall (lambda (t) (mem t l2)) l1)) |