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|
(define-library (csc list)
(export
all
any
filter
foldl
foldr
intersperse
map-maybe)
(import (scheme base))
(begin
(define (any1 f l)
(and (not (null? l))
(or (f (car l))
(any1 f (cdr l)))))
(define (any f . ls)
(and (not (any1 null? ls))
(or (apply f (map car ls))
(apply any f (map cdr ls)))))
(define (all f . ls)
(or (any null? ls)
(and (apply f (map car ls))
(apply all f (map cdr ls)))))
(define (foldl f acc . ls)
(if (any null? ls)
acc
(apply foldl f (apply f acc (map car ls)) (map cdr ls))))
(define (foldr f acc . ls)
(if (any null? ls)
acc
(apply f (append (map car ls) (list (apply foldr f acc (map cdr ls)))))))
(define (map-maybe f l)
(foldr
(lambda (x acc)
(define fx (f x))
(if fx
(cons fx acc)
acc))
'()
l))
(define (filter f l)
(foldr
(lambda (x acc)
(if (f x)
(cons x acc)
acc))
'()
l))
(define (intersperse sep l)
(if (null? l)
'()
(cons (car l)
(foldr
(lambda (x acc)
(cons sep (cons x acc)))
'()
(cdr l)))))))
|
