[Gauche]シーザー暗号

caesar.scm

(define base (string->list "ABCDEFGHIJKLMNOPQRSTUVWXYZ"))
(define base2 (string->list "abcdefghijklmnopqrstuvwxyz"))

(define (caesar lst n)
  (let ((solve (append (drop base n) (take base n)))
		(solve2 (append (drop base2 n) (take base2 n))))
	(let loop ((lst lst)
			   (n 0)
			   (result '()))
	  (cond
		((null? lst)
		 (reverse result))
		((> n 25)
		 (loop (cdr lst) 0 result))
		((eq? (car lst) (list-ref base n))
		 (loop (cdr lst) 0 (cons (list-ref solve n) result)))
		((eq? (car lst) (list-ref base2 n))
		 (loop (cdr lst) 0 (cons (list-ref solve2 n) result)))
		(else (loop lst (+ n 1) result))))))

;(define (main args)
;  (print (list->string (caesar (string->list "I Love you") 3))))
;=> LOryhbrx