std::lcm

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Numerics library

Common mathematical functions
Mathematical special functions (C++17)
Mathematical constants (C++20)
Basic linear algebra algorithms (C++26)
Floating-point environment (C++11)
Complex numbers
Numeric array (valarray)
Pseudo-random number generation
Factor operations
gcd (C++17)	lcm (C++17)
Interpolations
midpoint (C++20)	lerp (C++20)
Saturation arithmetic
add_sat (C++26) sub_sat (C++26) saturate_cast (C++26)	mul_sat (C++26) div_sat (C++26)
Generic numeric operations
iota (C++11) ranges::iota (C++23) accumulate inner_product adjacent_difference partial_sum	reduce (C++17) transform_reduce (C++17) inclusive_scan (C++17) exclusive_scan (C++17) transform_inclusive_scan (C++17) transform_exclusive_scan (C++17)
Bit operations
has_single_bit (C++20)     bit_cast (C++20) bit_ceil (C++20) bit_floor (C++20) bit_width (C++20) rotl (C++20) rotr (C++20)	popcount (C++20) countl_zero (C++20) countl_one (C++20) countr_zero (C++20) countr_one (C++20) byteswap (C++23) endian (C++20)

 

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

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

Parameters

m, n

-

integer values

Return value

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

The behavior is undefined if |m|, |n|, or the least common multiple of |m| and |n| is not representable as a value of type std::common_type_t<M, N>.

Exceptions

Throws no exceptions.

Notes

Feature-test macro	Value	Std	Feature
__cpp_lib_gcd_lcm

Example

Run this code

#include <numeric>
#include <iostream>
 
#define OUT(...) std::cout << #__VA_ARGS__ << " = " << __VA_ARGS__ << '\n'
 
constexpr auto lcm(auto x, auto y) {
    return std::lcm(x,y);
}
constexpr auto lcm(auto head, auto...tail) {
    return std::lcm(head, lcm(tail...));
}
 
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));
 
    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));
}

Output:

lcm(2*3, 3*4, 4*5) = 60
lcm(2*3*4, 3*4*5, 4*5*6) = 120
lcm(2*3*4, 3*4*5, 4*5*6, 5*6*7) = 840

See also

gcd (C++17)

computes the greatest common divisor of two integers (function template)