std::lcm

Since C++17

Header: <numeric>

Computes the least common multiple of the integers m and n.

# Declarations

template< class M, class N >
constexpr std::common_type_t<M, N> lcm( M m, N n );

(since C++17)

# Parameters

# Return value

If either m or n is zero, returns zero. Otherwise, returns the least common multiple of |m| and |n|.

# Notes

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

# Example

#include <iostream>
#include <numeric>
 
#define OUT(...) std::cout << #__VA_ARGS__ << " = " << __VA_ARGS__ << '\n'
 
constexpr auto lcm(auto x, auto... xs)
{
    return ((x = std::lcm(x, xs)), ...);
}
 
int main()
{
    constexpr int p{2 * 2 * 3};
    constexpr int q{2 * 3 * 3};
    static_assert(2 * 2 * 3 * 3 == std::lcm(p, q));
    static_assert(225 == std::lcm(45, 75));
 
    static_assert(std::lcm( 6,  10) == 30);
    static_assert(std::lcm( 6, -10) == 30);
    static_assert(std::lcm(-6, -10) == 30);
 
    static_assert(std::lcm( 24, 0) == 0);
    static_assert(std::lcm(-24, 0) == 0);
 
    OUT(lcm(2 * 3, 3 * 4, 4 * 5));
    OUT(lcm(2 * 3 * 4, 3 * 4 * 5, 4 * 5 * 6));
    OUT(lcm(2 * 3 * 4, 3 * 4 * 5, 4 * 5 * 6, 5 * 6 * 7));
}

# See also