diff options
| -rw-r--r-- | src/pow.c | 11 |
1 files changed, 7 insertions, 4 deletions
@@ -38,8 +38,7 @@ mpfr_pow_is_exact (mpfr_ptr z, mpfr_srcptr x, mpfr_srcptr y, mpfr_rnd_t rnd_mode, int *inexact) { mpz_t a, c; - mpfr_exp_t d, b; - unsigned long i; + mpfr_exp_t d, b, i; int res; MPFR_ASSERTD (!MPFR_IS_SINGULAR (y)); @@ -52,7 +51,9 @@ mpfr_pow_is_exact (mpfr_ptr z, mpfr_srcptr x, mpfr_srcptr y, if (MPFR_IS_NEG (y)) return 0; /* x is not a power of two => x^-y is not exact */ - /* compute d such that y = c*2^d with c odd integer */ + /* Compute d such that y = c*2^d with c odd integer. + Since c comes from a regular MPFR number, due to the constraints on the + exponent and the precision, there can be no integer overflow below. */ mpz_init (c); d = mpfr_get_z_2exp (c, y); i = mpz_scan1 (c, 0); @@ -62,7 +63,9 @@ mpfr_pow_is_exact (mpfr_ptr z, mpfr_srcptr x, mpfr_srcptr y, /* Since y is not an integer, d is necessarily < 0 */ MPFR_ASSERTD (d < 0); - /* Compute a,b such that x=a*2^b */ + /* Compute a,b such that x=a*2^b. + Since a comes from a regular MPFR number, due to the constrainst on the + exponent and the precision, there can be no integer overflow below. */ mpz_init (a); b = mpfr_get_z_2exp (a, x); i = mpz_scan1 (a, 0); |