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std::gcd

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.

Parameters

m, n

integer values

Return value

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

Remarks

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.

Exceptions

Throws no exceptions.

Notes

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

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);
}