mirror/guile
mirror/guile
1
Fork 0
mirror of https://git.savannah.gnu.org/git/guile.git synced 2025-06-10 14:00:21 +02:00
Code Activity

(scm_integer_length): On negative bignums, adjust

Browse source 
mpz_sizeinbase to account for it looking at absolute value where we
want ones-complement.
This commit is contained in:
Kevin Ryde 2003-05-10 00:05:51 +00:00
parent a4d9ffa1ed
commit 2c57607ca8
1 changed files with 7 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

7
libguile/numbers.c
View file

@ -1438,7 +1438,14 @@ SCM_DEFINE (scm_integer_length, "integer-length", 1, 0, 0,
};
return SCM_MAKINUM (c - 4 + l);
} else if (SCM_BIGP (n)) {
/* mpz_sizeinbase looks at the absolute value of negatives, whereas we
want a ones-complement. If n is ...111100..00 then mpz_sizeinbase is
1 too big, so check for that and adjust. */
size_t size = mpz_sizeinbase (SCM_I_BIG_MPZ (n), 2);
if (mpz_sgn (SCM_I_BIG_MPZ (n)) < 0
&& mpz_scan0 (SCM_I_BIG_MPZ (n), /* no 0 bits above the lowest 1 */
mpz_scan1 (SCM_I_BIG_MPZ (n), 0)) == ULONG_MAX)
size--;
scm_remember_upto_here_1 (n);
return SCM_MAKINUM (size);
} else {