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

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This commit is contained in:
Nick Thompson
2018-12-04 11:27:37 -07:00
parent 51b259da19
commit 080f2bdfdc
1 changed files with 6 additions and 6 deletions
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12
include/boost/integer/mod_inverse.hpp
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@ -22,24 +22,24 @@ namespace boost { namespace integer {
template<class Z> template<class Z>
Z mod_inverse(Z a, Z modulus) Z mod_inverse(Z a, Z modulus)
{ {
if (modulus < 2) if (modulus < Z(2))
{ {
BOOST_THROW_EXCEPTION(std::domain_error("Modulus must be > 1.")); BOOST_THROW_EXCEPTION(std::domain_error("Modulus must be > 1."));
} }
// make sure a < modulus: // make sure a < modulus:
a = a % modulus; a = a % modulus;
if (a == 0) if (a == Z(0))
{ {
// a doesn't have a modular multiplicative inverse: // a doesn't have a modular multiplicative inverse:
return 0; return Z(0);
} }
euclidean_result_t<Z> u = extended_euclidean(a, modulus); 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: // 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; u.x += modulus;
} }