ikarus/benchmarks.larceny/src/dderiv.scm

87 lines
2.0 KiB
Scheme

;;; DDERIV -- Table-driven symbolic derivation.
;;; Returns the wrong answer for quotients.
;;; Fortunately these aren't used in the benchmark.
(define (lookup key table)
(let loop ((x table))
(if (null? x)
#f
(let ((pair (car x)))
(if (eq? (car pair) key)
pair
(loop (cdr x)))))))
(define properties '())
(define (get key1 key2)
(let ((x (lookup key1 properties)))
(if x
(let ((y (lookup key2 (cdr x))))
(if y
(cdr y)
#f))
#f)))
(define (put key1 key2 val)
(let ((x (lookup key1 properties)))
(if x
(let ((y (lookup key2 (cdr x))))
(if y
(set-cdr! y val)
(set-cdr! x (cons (cons key2 val) (cdr x)))))
(set! properties
(cons (list key1 (cons key2 val)) properties)))))
(define (my+dderiv a)
(cons '+
(map dderiv (cdr a))))
(define (my-dderiv a)
(cons '-
(map dderiv (cdr a))))
(define (*dderiv a)
(list '*
a
(cons '+
(map (lambda (a) (list '/ (dderiv a) a)) (cdr a)))))
(define (/dderiv a)
(list '-
(list '/
(dderiv (cadr a))
(caddr a))
(list '/
(cadr a)
(list '*
(caddr a)
(caddr a)
(dderiv (caddr a))))))
(put '+ 'dderiv my+dderiv)
(put '- 'dderiv my-dderiv)
(put '* 'dderiv *dderiv)
(put '/ 'dderiv /dderiv)
(define (dderiv a)
(if (not (pair? a))
(if (eq? a 'x) 1 0)
(let ((f (get (car a) 'dderiv)))
(if f
(f a)
(fatal-error "No derivation method available")))))
(define (main . args)
(run-benchmark
"dderiv"
dderiv-iters
(lambda (result)
(equal? result
'(+ (* (* 3 x x) (+ (/ 0 3) (/ 1 x) (/ 1 x)))
(* (* a x x) (+ (/ 0 a) (/ 1 x) (/ 1 x)))
(* (* b x) (+ (/ 0 b) (/ 1 x)))
0)))
(lambda (a) (lambda () (dderiv a)))
'(+ (* 3 x x) (* a x x) (* b x) 5)))