< cpp‎ | numeric
Defined in header <numeric>
template< class M, class N >
constexpr std::common_type_t<M, N> gcd( M m, N n );
(since C++17)

Computes the greatest common divisor of the integers m and n.

If either M or N is not an integer type, or if either is (possibly cv-qualified) bool, the program is ill-formed.

If either |m| or |n| is not representable as a value of type std::common_type_t<M, N>, the behavior is undefined.


[edit] Parameters

m, n - integer values

[edit] Return value

If both m and n are zero, returns zero. Otherwise, returns the greatest common divisor of |m| and |n|.

[edit] Exceptions

Throws no exceptions.

[edit] Notes

Feature-test macro Value Std Feature
__cpp_lib_gcd_lcm 201606L (C++17) std::gcd, std::lcm

[edit] Example

#include <numeric>
int main()
    constexpr int p{2 * 2 * 3};
    constexpr int q{2 * 3 * 3};
    static_assert(2 * 3 == std::gcd(p, q));
    static_assert(std::gcd( 6,  10) == 2);
    static_assert(std::gcd( 6, -10) == 2);
    static_assert(std::gcd(-6, -10) == 2);
    static_assert(std::gcd( 24, 0) == 24);
    static_assert(std::gcd(-24, 0) == 24);

[edit] See also

computes the least common multiple of two integers
(function template) [edit]