PAIP 2.6

どうもうまいこと書けない。。それに名前付けがいつも悪い。

	;; PAIP 2.6 P.41
	(define (combine-all xlis ylis)
	(mappend (lambda (y)
	(map (lambda (x)
	(append x y)) xlis))
	ylis))
	(print (combine-all (map list '(a b c))(map list '(1 2 3))))
	;; ((a 1) (b 1) (c 1) (a 2) (b 2) (c 2) (a 3) (b 3) (c 3))
	;; (cross-combine '(1 2 3)'(a b c))
	;; ((1 a) (2 a) (3 a) (1 b) (2 b) (3 b) (1 c) (2 c) (3 c))
	(define (cross-combine xlis ylis)
	(mappend (lambda (y)
	(map (lambda (x)
	(list x y)) xlis))
	ylis))
	;; (add-combine-elements (cross-combine '(1 2 3)'(a b c))
	;; '(100 200 300))
	;; ((1 a 100) (2 a 100) (3 a 100) (1 b 100) (2 b 100) (3 b 100) (1 c 100) (2 c 100) (3 c 100) (1 a 200) (2 a 200) (3 a 200) (1 b 200) (2 b 200) (3 b 200) (1 c 200) (2 c 200) (3 c 200) (1 a 300) (2 a 300) (3 a 300) (1 b 300) (2 b 300) (3 b 300) (1 c 300) (2 c 300) (3 c 300))
	(define (add-combine-elements comb elements)
	(mappend (lambda (c)
	(map (lambda (e)
	(append e (list c))) comb))
	elements))
	(define (cross-combine xls yls . opt)
	(let-optionals* opt ((kons list))
	(mappend (lambda (y)
	(map (lambda (x)
	(kons x y)) xls))
	yls)))
	(define (add-combine-elements comb elements)
	(cross-combine comb elements (lambda (e c)
	(append e (list c)))))
	(define (cross-combines ls1 ls2 . lss)
	(let rec ((lss lss)(comb (cross-combine ls1 ls2)))
	(if (null? lss)
	comb
	(rec (cdr lss)
	(add-combine-elements comb (car lss))))))
	;; (print (combine-all (map list '(a b c))(map list '(1 2 3))))
	;; ((a 1) (b 1) (c 1) (a 2) (b 2) (c 2) (a 3) (b 3) (c 3))
	(define (combine-all xlis ylis)
	(cross-combine xlis ylis append))
	(print (cross-combines '(a b c)'(1 2 3)'(100 200 300)))
	;; ((a 1 100) (b 1 100) (c 1 100)
	;; (a 2 100) (b 2 100) (c 2 100)
	;; (a 3 100) (b 3 100) (c 3 100)
	;; (a 1 200) (b 1 200) (c 1 200)
	;; (a 2 200) (b 2 200) (c 2 200)
	;; (a 3 200) (b 3 200) (c 3 200)
	;; (a 1 300) (b 1 300) (c 1 300)
	;; (a 2 300) (b 2 300) (c 2 300)
	;; (a 3 300) (b 3 300) (c 3 300))
	(print (cross-combines '(a b c)'(#f #t)'(1 2 3)'(100 200 300)))
	;; ((a #f 1 100) (b #f 1 100) (c #f 1 100)
	;; (a #t 1 100) (b #t 1 100) (c #t 1 100)
	;; (a #f 2 100) (b #f 2 100) (c #f 2 100)
	;; (a #t 2 100) (b #t 2 100) (c #t 2 100)
	;; (a #f 3 100) (b #f 3 100) (c #f 3 100)
	;; (a #t 3 100) (b #t 3 100) (c #t 3 100)
	;; (a #f 1 200) (b #f 1 200) (c #f 1 200)
	;; (a #t 1 200) (b #t 1 200) (c #t 1 200)
	;; (a #f 2 200) (b #f 2 200) (c #f 2 200)
	;; (a #t 2 200) (b #t 2 200) (c #t 2 200)
	;; (a #f 3 200) (b #f 3 200) (c #f 3 200)
	;; (a #t 3 200) (b #t 3 200) (c #t 3 200)
	;; (a #f 1 300) (b #f 1 300) (c #f 1 300)
	;; (a #t 1 300) (b #t 1 300) (c #t 1 300)
	;; (a #f 2 300) (b #f 2 300) (c #f 2 300)
	;; (a #t 2 300) (b #t 2 300) (c #t 2 300)
	;; (a #f 3 300) (b #f 3 300) (c #f 3 300)
	;; (a #t 3 300) (b #t 3 300) (c #t 3 300))

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読むペースと書くペースが合わない。。どんどん先を読んで、後から書いて、2度読むことになってなんとも。。だがそれがいい。