Marc,
> If the function mpz_get_ld is provided, I expect it to work for the whole
> (exponent) range of long double value, not just the range of double.
> Should we first do something about large z, then apply your method and fix
> the result with ldexpl?
you are right. Here is an improved version.
long double
mpz_get_ld (mpz_t z)
{
long double h, l;
long int e;
mpz_t tmp;
h = (long double) mpz_get_d_2exp (&e, z); /* 0.5 <= |h| < 1 */
h = ldexpl (h, 53); /* now h is an integer */
e -= 53;
mpz_init (tmp);
mpz_set_d (tmp, (double) h); /* exact */
if (e >= 0)
mpz_mul_2exp (tmp, tmp, e);
else
mpz_div_2exp (tmp, tmp, -e);
mpz_sub (tmp, z, tmp);
h = ldexpl (h, e);
l = (long double) mpz_get_d_2exp (&e, tmp);
l = ldexpl (l, e);
mpz_clear (tmp);
return h + l;
}
Paul
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