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Fixing integer-length to use inline C

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Koz Ross 2017-02-10 17:23:57 +13:00
parent c13f37e3b5
commit a024126f7b
1 changed files with 11 additions and 3 deletions
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14
srfi/60.scm
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@ -108,11 +108,19 @@
(define bit-count logcount)
(define (integer-length x)
(exact (ceiling (log (+ x 1) 2))))
(define-c integer-length
"(void* data, int argc, closure _, object k, object x)"
"Cyc_check_int(data, x);
int input = (int)unbox_number(x);
int res = 0;
while (input) {
res++;
input >>= 1;
};
return_closcall1(data, k, obj_int2obj(res));")
(define (log2-binary-factors n)
(- (integer-length (logand n (- n))) 1))
(- (integer-length (raw-logand n (- n))) 1))
(define first-set-bit log2-binary-factors)