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;;; File:         dderiv.sc
;;; Description:  DDERIV benchmark from the Gabriel tests
;;; Author:       Vaughan Pratt
;;; Created:      8-Apr-85
;;; Modified:     10-Apr-85 14:53:29 (Bob Shaw)
;;;               23-Jul-87 (Will Clinger)
;;;               9-Feb-88 (Will Clinger)
;;;               21-Mar-94 (Qobi)
;;;               31-Mar-98 (Qobi)
;;;		  26-Mar-00 (flw)
;;; Language:     Scheme (but see note below)
;;; Status:       Public Domain
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;; Note:  This benchmark uses property lists.  The procedures that must
;;; be supplied are get and put, where (put x y z) is equivalent to Common
;;; Lisp's (setf (get x y) z).

;;; DDERIV -- Symbolic derivative benchmark written by Vaughan Pratt.

;;; This benchmark is a variant of the simple symbolic derivative program
;;; (DERIV). The main change is that it is `table-driven.'  Instead of using a
;;; large COND that branches on the CAR of the expression, this program finds
;;; the code that will take the derivative on the property list of the atom in
;;; the CAR position. So, when the expression is (+ . <rest>), the code
;;; stored under the atom '+ with indicator DERIV will take <rest> and
;;; return the derivative for '+. The way that MacLisp does this is with the
;;; special form: (DEFUN (FOO BAR) ...). This is exactly like DEFUN with an
;;; atomic name in that it expects an argument list and the compiler compiles
;;; code, but the name of the function with that code is stored on the
;;; property list of FOO under the indicator BAR, in this case. You may have
;;; to do something like:

;;; :property keyword is not Common Lisp.


(define (dderiv-aux a) (list '/ (dderiv a) a))

(define (+dderiv a) (cons '+ (map dderiv a)))

(put '+ 'dderiv +dderiv)    ; install procedure on the property list

(define (-dderiv a) (cons '- (map dderiv a)))

(put '- 'dderiv -dderiv)    ; install procedure on the property list

(define (*dderiv a) (list '* (cons '* a) (cons '+ (map dderiv-aux a))))

(put '* 'dderiv *dderiv)    ; install procedure on the property list

(define (/dderiv a)
 (list '-
       (list '/ (dderiv (car a)) (cadr a))
       (list '/
	     (car a)
	     (list '* (cadr a) (cadr a) (dderiv (cadr a))))))

(put '/ 'dderiv /dderiv)    ; install procedure on the property list

(define (dderiv a)
 (cond ((not (pair? a)) (cond ((eq? a 'x) 1) (else 0)))
       (else (let ((dderiv (get (car a) 'dderiv)))
	      (cond (dderiv (dderiv (cdr a)))
		    (else 'error))))))

(define (run)
 (do ((i 0 (+ i 1))) ((= i 1000))
  (dderiv '(+ (* 3 x x) (* a x x) (* b x) 5))
  (dderiv '(+ (* 3 x x) (* a x x) (* b x) 5))
  (dderiv '(+ (* 3 x x) (* a x x) (* b x) 5))
  (dderiv '(+ (* 3 x x) (* a x x) (* b x) 5))
  (dderiv '(+ (* 3 x x) (* a x x) (* b x) 5))))


;(time (do ((i 10 (- i 1))) ((zero? i)) (run)))
(run)
(display (dderiv '(+ (* 3 x x) (* a x x) (* b x) 5)))
(newline)