ikarus/benchmarks/rnrs-benchmarks/ntakl.ss

50 lines
1.3 KiB
Scheme

;;; NTAKL -- The TAKeuchi function using lists as counters,
;;; with an alternative boolean expression.
(library (rnrs-benchmarks ntakl)
(export main)
(import (rnrs) (rnrs-benchmarks))
(define (listn n)
(if (= n 0)
'()
(cons n (listn (- n 1)))))
(define l18 (listn 18))
(define l12 (listn 12))
(define l6 (listn 6))
(define (mas x y z)
(if (not (shorterp y x))
z
(mas (mas (cdr x) y z)
(mas (cdr y) z x)
(mas (cdr z) x y))))
; Part of the fun of this benchmark is seeing how well the compiler
; can understand this ridiculous code, which dates back to the original
; Common Lisp. So it probably isn't a good idea to improve upon it.
#;
(define (shorterp x y)
(and (not (null? y))
(or (null? x)
(shorterp (cdr x)
(cdr y)))))
; But SML/NJ runs this benchmark about 15 times as fast when the
; code above is rewritten as follows, so I tried it for Scheme also.
(define (shorterp x y)
(cond ((null? y) #f)
((null? x) #t)
(else
(shorterp (cdr x) (cdr y)))))
(define (main . args)
(run-benchmark
"ntakl"
takl-iters
(lambda (result) (equal? result '(7 6 5 4 3 2 1)))
(lambda () (lambda () (mas l18 l12 l6))))))