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;; {\documentstyle[a4j]{jarticle}}
;; {\src2tex{texfont=bf}}
;; [] 뤪ɴȬ֤ʤ¼ϤδߤˤäƤ
;; Ȭ֤ˤϡǤ줿٥Ĥ餤϶ä˥ȥ꤬Ѥޤ
;; Ƥ¼˻ԤΩĤΤǡλԤǥ٥Ĥȥ˥ȥȤ
;; 櫓Ǥ롣θɴˤäʤĤƤޤäĥͤΥ
;; ˤ˥ȥ٤ʤ֤ơ夤Ƥ
;; {\src2tex{texfont=rm}}
;; ơΤۤȤˤϰۤξĤʤǤäǡɴ
;; ϥ˥ȥꡢ٥ġĥͤΤ٤ƤδߤرФʤФʤʤ
;; äȤˡѾäΤǡĤ뤪ɴʳ
;; ٤˱٤Τϡ˥ȥꡢ٥ġĥͤΤΤɤ줫Ĥä
;; ȤʢΤؤä˥ȥϡɴʤʤȥ٥Ĥ٤
;; ޤ˥ĥͤΥϤɴܤΥȡ˥ȥ٤Ƥ
;; ޤ
;; {\src2tex{texfont=bf}}
;; ɤä顢ɴϼɤ˥ȥꡢ٥ġĥͤΤ٤Ƥ
;; ¦δߤ˱٤
;; {\src2tex{texfont=sc}}
;; farmer+hen.scm by Kazuo AMANO
;; east-side-state is represented by list $(w\ x\ y\ z)$ where each $w, x, y, z = 0$ or $1$
;; example: {\null\[
;; \begin{array}{l}
;; (1\ 1\ 1\ 1) = {\rm (farmer\ hen\ cabbage\ fox)-state}\\
;; (0\ 1\ 0\ 1) = {\rm (none\ hen\ none\ fox)-state}\\
;; (1\ 0\ 1\ 0) = {\rm (farmer\ none\ cabbage\ none)-state}
;; \end{array}
;; \]}
;; initial-state = (1 1 1 1)
;; state-sequence = (... state2 state1 initial-state)
;; state-tree = (... state-sequece2 state-sequence1 state-sequence0)
; {\src2tex{htab=4 textfont=it texfont=rm}}
; ؤΰư
(define (west->east x seq)
(let* ((y (car seq)) (fa (car y)) (he (cadr y)) (ca (caddr y)) (fo (cadddr y)))
(cond ((= fa 0) (cons '() seq))
(else (cond ((and (equal? x 'hen) (= he 1)) (cons (list 0 0 ca fo) seq))
((and (equal? x 'cabbage) (= ca 1)) (cons (list 0 he 0 fo) seq))
((and (equal? x 'fox) (= fo 1)) (cons (list 0 he ca 0) seq))
(else (cons '() seq)))))))
; {\src2tex{htab=4 textfont=it texfont=rm}}
; 줫ؤΰư
(define (west<-east x seq)
(let* ((y (car seq)) (fa (car y)) (he (cadr y)) (ca (caddr y)) (fo (cadddr y)))
(cond ((= fa 1) (cons '() seq))
(else (cond ((and (equal? x 'hen) (= he 0)) (cons (list 1 1 ca fo) seq))
((and (equal? x 'cabbage) (= ca 0)) (cons (list 1 he 1 fo) seq))
((and (equal? x 'fox) (= fo 0)) (cons (list 1 he ca 1) seq))
((equal? x 'none) (cons (list 1 he ca fo) seq))
(else (cons '() seq)))))))
; {\src2tex{htab=4 textfont=sl texfont=rm}}
; λȽؿ
(define (finished? tree)
(let finished1? ((x tree))
(cond ((null? x) #f)
((equal? (caar x) '(0 0 0 0)) #t)
(else (finished1? (cdr x))))))
; {\src2tex{htab=4 textfont=sl texfont=rm}}
; Ŭ branch ڤȤؿ
(define (rm-bad-seq tree)
(let rm-bad-seq1 ((x tree) (y '()))
(cond ((null? x) y)
((null? (caar x)) (rm-bad-seq1 (cdr x) y))
((equal? (caar x) '(1 0 1 0)) (rm-bad-seq1 (cdr x) y))
((equal? (caar x) '(1 0 0 1)) (rm-bad-seq1 (cdr x) y))
((equal? (caar x) '(0 1 1 0)) (rm-bad-seq1 (cdr x) y))
((equal? (caar x) '(0 1 0 1)) (rm-bad-seq1 (cdr x) y))
((equal? (caar x) '(1 1 1 1)) (rm-bad-seq1 (cdr x) y))
(else (rm-bad-seq1 (cdr x) (cons (car x) y))))))
; {\src2tex{htab=4 textfont=sl texfont=bf}}
; branch Ĺؿ
(define (mkseq seq)
(rm-bad-seq
(list (west->east 'hen seq) (west->east 'cabbage seq) (west->east 'fox seq)
(west<-east 'hen seq) (west<-east 'cabbage seq) (west<-east 'fox seq)
(west<-east 'none seq))))
; {\src2tex{htab=4 textfont=tt texfont=bf}}
; tree ؿ
(define (mktree initial-state)
(let mktree1 ((x (list (list initial-state))))
(cond ((finished? x) x)
(else (mktree1 (let mktree2 ((x1 x) (x2 '()))
(cond ((null? x1) x2)
(else (mktree2 (cdr x1) (append x2 (mkseq (car x1))))))))))))
; {\src2tex{htab=4 textfont=bf texfont=bf}}
; main ؿ
(define (main-func)
(let display-answer ((x (mktree '(1 1 1 1))))
(cond ((null? x) (newline))
(else (cond ((equal? (caar x) '(0 0 0 0)) (display (car x)) (newline)))
(display-answer (cdr x))))))
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