vallog: Gauche group-sequence と L-99 の L09

2010/07/29

マイペースに L-99 を続けてきましたが、L27 がなかなか解けなくて滞っています。。

ところで、掲題の通り L09 については、Gauche に group-sequence というものがあったのでメモ。

	(use gauche.sequence)

	(group-sequence '(1 1 1 2 3 4 4 2 2 3 1 1 3))
	;; ((1 1 1) (2) (3) (4 4) (2 2) (3) (1 1) (3))

	(group-sequence '(a a a a b c c a a d e e e e))
	;; ((a a a a) (b) (c c) (a a) (d) (e e e e))

view raw group-sequence.scm hosted with ❤ by GitHub

自分で書いたのは、こんな感じでした。

	;; P09 (**) Pack consecutive duplicates of list elements into sublists.
	;; If a list contains repeated elements they should be placed in separate sublists.

	;; Example:
	;; * (pack '(a a a a b c c a a d e e e e))
	;; ((A A A A) (B) (C C) (A A) (D) (E E E E))

	(define (pack ls . opt)
	(let-optionals* opt ((eq? eq?))
	(pair-fold-right
	(lambda (pr acc)
	(apply acons (car pr)
	(if (or (null? acc)
	(not (eq? (car pr)(caar acc))))
	`(() ,acc)
	`(,(car acc),(cdr acc)))))
	'() ls)))

	(pack '(a a a a b c c a a d e e e e))
	;; ((a a a a) (b) (c c) (a a) (d) (e e e e))
	(pack '(1))
	;; ((1))
	(pack '(1 2 3 1 2 3))
	;; ((1) (2) (3) (1) (2) (3))
	(pack '())
	;; ()
	(pack (map (cut cons <> '())
	'(a a a a b c c a a d e e e e)))
	;; (((a)) ((a)) ((a)) ((a)) ((b)) ((c)) ((c)) ((a)) ((a)) ((d)) ((e)) ((e)) ((e)) ((e)))
	(pack (map (cut cons <> '())
	'(a a a a b c c a a d e e e e)) equal?)
	;; (((a) (a) (a) (a)) ((b)) ((c) (c)) ((a) (a)) ((d)) ((e) (e) (e) (e)))

view raw L09.scm hosted with ❤ by GitHub

vallog