;; ------------------------------------------------------------------
;; The Machine-Human Interface (BIOS)

(define abort (lambda (x) (error 'abort "undefined")))

(define walk
  (lambda ()
    (call-with-current-continuation
      (lambda (k) (set! abort k)
	(set-pc! 0)
	(shell)))))

(define shell
  (local ((define install
	    (lambda (value)
	      (if (value? value)
		  (begin
		    (set-mem! (get-pc) value)
		    (print-cell (get-pc))
		    (newline)
		    (get&inc-pc))
		  (printf "Warning: not a command!~n")))))
    (lambda ()
      (begin
	(print-cell (get-pc))
	(printf " % ")  ; input prompt
	(local ([define command (read)])
	  (cond
	    ((cons? command) (install (assemble command)))
	    ((number? command) (install command))
	    ((symbol? command) ((find-command command the-command-list)))
	    (else (default-action))))
	(shell)))))

(define find-command
  (lambda (command command-list)
    (local ((define r (assq command command-list)))
      (if r (entry-action r) default-action))))

(define entry-action caddr)
(define entry-description cadr)