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Optimize two-list srfi-1 map

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* module/srfi/srfi-1.scm (map): Optimize the two-list variant.
This commit is contained in:
Andy Wingo 2014-04-01 20:52:15 +02:00
parent 545274a035
commit f082c5f30a
1 changed files with 17 additions and 0 deletions
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17
module/srfi/srfi-1.scm
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@ -572,6 +572,23 @@ has just one element then that's the return value."
(map1 (cdr in) (cons (f (car in)) out)) (map1 (cdr in) (cons (f (car in)) out))
(reverse! out)))) (reverse! out))))
((f l1 l2)
(check-arg procedure? f map)
(let* ((len1 (length+ l1))
(len2 (length+ l2))
(len (if (and len1 len2)
(min len1 len2)
(or len1 len2))))
(unless len
(scm-error 'wrong-type-arg "map"
"Args do not contain a proper (finite) list: ~S"
(list (list l1 l2)) #f))
(let map2 ((l1 l1) (l2 l2) (out '()) (len len))
(if (zero? len)
(reverse! out)
(map2 (cdr l1) (cdr l2)
(cons (f (car l1) (car l2)) out) (1- len))))))
((f l1 . rest) ((f l1 . rest)
(check-arg procedure? f map) (check-arg procedure? f map)
(let ((len (fold (lambda (ls len) (let ((len (fold (lambda (ls len)