bf-readable.lisp

(let ((tape (make-array 30000))
      (pointer 0)
      (source-file (open (cadr *posix-argv*))))

  (defun current ()
    (aref tape pointer))

  (defun read-source ()
    (case (read-char source-file nil :eof)
      (#\< (cons (lambda ()
                   (decf pointer))
                 (read-source)))
      (#\> (cons (lambda ()
                   (incf pointer))
                 (read-source)))
      (#\+ (cons (lambda ()
                   (incf (aref tape pointer)))
                 (read-source)))
      (#\- (cons (lambda ()
                   (decf (aref tape pointer)))
                 (read-source)))
      (#\. (cons (lambda ()
                   (princ (code-char (current))))
                 (read-source)))
      (#\, (cons (lambda ()
                   (force-output)
                   (setf (aref tape pointer)
                         (char-code (read-char nil nil #\Nul))))
                 (read-source)))
      (#\[ (cons (read-source)
                 (read-source)))
      (#\] '())
      (:eof (cons #'exit '()))
      (t (read-source))))

  (defun eval-cmd (cmd)
    (if (consp cmd)
      (when (> (current) 0)
        (eval-bf cmd))
      (funcall cmd)))

  (defun eval-bf (commands)
    (mapc #'eval-cmd commands)
    (when (> (current) 0)
      (eval-bf commands)))

  (eval-bf (read-source)))