#!/bin/bash
PROG=${0%.jl}
[ \! -f $PROG.jlc -o $0 -nt $PROG.jlc ] &&
    rep --batch --no-rc -l compiler -f compile-batch $0
exec rep "$PROG.jlc" "$@"
!#

;;; $Id: ackermann.rep,v 1.5 2000/12/25 18:07:30 doug Exp $
;;; http://www.bagley.org/~doug/shootout/

(define (ack M N)
  (cond ((= M 0) (+ N 1))
        ((= N 0) (ack (- M 1) 1))
        (t (ack (- M 1) (ack M (- N 1))))))
  
(let* ((arg (get-command-line-option "--num" t))
       (n (if arg (read-from-string arg) 1)))
  (max-lisp-depth 2500)
  (format standard-output "Ack(3,%d): %d\n" n (ack 3 n)))

;; CMUCL implementation

(defun fast-ack (m n)
  (declare (fixnum n m) (optimize (speed 3) (debug 0) (safety 0)))
  (the fixnum
    (cond
     ((zerop m) (the fixnum (1+ n)))
     ((zerop n) (the fixnum (fast-ack (1- m) 1)))
     (t (the fixnum (fast-ack (1- m) (the fixnum (fast-ack m (1- n)))))))))

;(defun ack (m n)
;  (cond
;   ((zerop m) (1+ n))
;   ((zerop n) (ack (1- m) 1))
;   (t (ack (1- m) (ack m (1- n))))))

;; my stupid implementation
(defun ack (m n)
  (if (and (= m 0) (/= n 0))
      (+ n 1)
    (if (and (/= m 0) (= n 0))
        (ack (- m 1) 1)
      (ack (- m 1) (ack m (- n 1))))))

;; BUG (ack 0 0) -> inf. loop

;; haskell def:
;; ack 0 n         = n+1
;; ack (m+1) 0     = ack m 1
;; ack (m+1) (n+1) = ack m (ack (m+1) n)

;; from comp.lang.lisp
(defun ackermann (m n)
  (declare (fixnum m n) (optimize (speed 3) (safety 0)))
  (cond
   ((zerop m) (1+ n))
   ((zerop n) (ackermann (1- m) 1))
   (t (ackermann (1- m) (ackermann m (1- n))))))

(princ (ackermann 3 4))