root/lang/zu/interpreter/scheme/trunk/lib/nt/zu.scm

;;;
;;; Zu - ported from yhara's Ruby implementation, by naoya_t
;;;
(define-module nt.zu
  (export
   zu-interpreter
   ))

(select-module nt.zu)

(use nt.textgraph) ;require "nt/textgraph"
(use srfi-1) ;filter

(define (zu-interpreter src)
  (let* ([tg (parse-textgraph src)]
                 [cells [tg'cells]]
                 [links [tg'links]])

        (define (ask msg)
          (display msg)
          (display " [y/n]\n> ")
          (let loop ()
                (case (read-char)
                  ((#\y #\Y) #t)
                  ((#\n #\N) #f)
                  (else (loop)))))
        
        (define (say msg)
          (print msg)
          #t)

        (define (eval inst)
          (case (car inst)
                ((ask) (ask (cadr inst)))
                ((say) (say (cadr inst)))
                (else #f)))

        (let loop ([i 0])
          (let* ([cell (ref cells i)]
                         [inst-str (string-append "(" [cell'content] ")")]
                         [inst (read-from-string inst-str)]
                         [ret (eval inst)]
                         [nexts (map cdr (filter (lambda (link) (= i (car link))) links))]
                         )
                (cond ((= 0 (length nexts)) 'done)
                          ((= 1 (length nexts)) (loop (car nexts)))
                          (else
                           (if ret
                                   (loop (cadr nexts))
                                   (loop (car nexts)))))
                ))))

(provide "nt/zu")
;;EOF