Take care of the case where integer type Z has explicit constructor.

This commit is contained in:
Nick Thompson
2018-12-04 11:27:37 -07:00
parent 51b259da19
commit 080f2bdfdc

View File

@ -22,24 +22,24 @@ namespace boost { namespace integer {
template<class Z>
Z mod_inverse(Z a, Z modulus)
{
if (modulus < 2)
if (modulus < Z(2))
{
BOOST_THROW_EXCEPTION(std::domain_error("Modulus must be > 1."));
}
// make sure a < modulus:
a = a % modulus;
if (a == 0)
if (a == Z(0))
{
// a doesn't have a modular multiplicative inverse:
return 0;
return Z(0);
}
euclidean_result_t<Z> u = extended_euclidean(a, modulus);
if (u.gcd > 1)
if (u.gcd > Z(1))
{
return 0;
return Z(0);
}
// x might not be in the range 0 < x < m, let's fix that:
while (u.x <= 0)
while (u.x <= Z(0))
{
u.x += modulus;
}