TSS letrec multirember

The Little Schemer でおなじみ multirember 。
Y combinator 使って書き直しましょう → Y combinator は letrec が代替に使えるよ、という無茶な流れ。

	;; chapter.12
	; multirember
	; standard
	(define (multirember a lat)
	(cond ((null? lat) '())
	((eq? a (car lat))(multirember a (cdr lat)))
	(else (cons (car lat)
	(multirember a (cdr lat))))))
	(multirember 'a '(a b c d a b c d))
	; fold
	(define (multirember a lat)
	(fold (lambda (e l)
	(if (eq? a e)
	l
	(cons e l)))
	'()
	lat))
	(multirember 1 '(1 2 3 1 2 3 1 2 3))
	; filter
	(use srfi-1)
	(define (multirember a lat)
	(filter (lambda (e)
	(not (eq? a e)))
	lat))
	(multirember 'a '(a b c a b c))
	; the seasoned schemer
	; y combinator
	(define Y
	(lambda (f)
	((lambda (g)
	(g g))
	(lambda (h)
	(f (lambda (x)
	((h h) x)))))))
	((Y (lambda (f)
	(lambda (n)
	(if (zero? n)
	1
	(* n (f (- n 1))))))) 5)
	(define multirember
	(lambda (a lat)
	((Y (lambda (mr)
	(lambda (lat)
	(cond ((null? lat) '())
	((eq? a (car lat))(mr (cdr lat)))
	(else (cons (car lat)
	(mr (cdr lat))))))))
	lat)))
	(multirember 'a '(a b c a b c a b c))
	(define multirember
	(lambda (a lat)
	(((lambda (f)
	((lambda (g)
	(g g))
	(lambda (h)
	(f (lambda (x)
	((h h) x))))))
	(lambda (mr)
	(lambda (lat)
	(cond ((null? lat) '())
	((eq? a (car lat))(mr (cdr lat)))
	(else (cons (car lat)
	(mr (cdr lat))))))))
	lat)))
	(multirember 1 '(1 2 1 2 1 2 3))
	;; length
	(define add1
	(lambda (n)
	(+ n 1)))
	;; (define length 'hoge)
	;; (display length)
	;; (define length
	;; (with-module gauche length))
	(define length
	(Y (lambda (length)
	(lambda (l)
	(cond ((null? l) 0)
	(else (add1 (length (cdr l)))))))))
	(length '(1 2 3))
	; letrec
	(define multirember
	(lambda (a lat)
	(letrec ((mr (lambda (l)
	(cond ((null? l) '())
	((eq? a (car l))(mr (cdr l)))
	(else (cons (car l)
	(mr (cdr l))))))))
	(mr lat))))
	(multirember 'a '(a b a b a b c a))

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