> In other words, this kind of stack-consuming implementation would be a
> perfectly practical, useful implementation in Racket
Even more than that -- in some cases the simple non-TCO version can be
faster than the usual TCO + reverse-the-accumulator thing. Here's a
random example:
Welcome to Racket v5.0.99.6.
-> (define (append1 l1 l2) (if (null? l1) l2 (cons (car l1) (append (cdr l1)
l2))))
-> (define (append2 l1 l2) (let loop ([l1 (reverse l1)] [l2 l2]) (if (null? l1)
l2 (loop (cdr l1) (cons (car l1) l2)))))
-> (define l1 (make-list 1000000 2))
-> (define l2 (make-list 1000000 2))
-> ,time 11 (for ([i (in-range 20)]) (append1 l1 l2))
;; run #1... -> #<void>
...
;; run #11... -> #<void>
;; 11 runs, 3 best/worst removed, 5 left for average:
;; cpu time: 2529ms = 453ms + 2076ms gc; real time: 2530ms
-> ,time 11 (for ([i (in-range 20)]) (append2 l1 l2))
;; run #1... -> #<void>
...
;; run #11... -> #<void>
;; 11 runs, 3 best/worst removed, 5 left for average:
;; cpu time: 4026ms = 896ms + 3130ms gc; real time: 4026ms
--
((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay:
http://barzilay.org/ Maze is Life!
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