Difference between revisions of "cpp/numeric/lcm"
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{{cpp/title|lcm}} | {{cpp/title|lcm}} | ||
{{cpp/numeric/navbar}} | {{cpp/numeric/navbar}} | ||
| − | {{ | + | {{ddcl|header=numeric|since=c++17| |
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template< class M, class N > | template< class M, class N > | ||
constexpr std::common_type_t<M, N> lcm( M m, N n ); | constexpr std::common_type_t<M, N> lcm( M m, N n ); | ||
}} | }} | ||
| − | |||
| − | Computes the least common multiple of the integers {{c|m}} and {{c|n}}. | + | Computes the {{enwiki|least common multiple}} of the integers {{c|m}} and {{c|n}}. |
| − | === Parameters === | + | If either {{tt|M}} or {{tt|N}} is not an integer type, or if either is (possibly cv-qualified) {{c|bool}}, the program is ill-formed. |
| + | |||
| + | The behavior is undefined if {{c|{{!}}m{{!}}}}, {{c|{{!}}n{{!}}}}, or the least common multiple of {{c|{{!}}m{{!}}}} and {{c|{{!}}n{{!}}}} is not representable as a value of type {{c|std::common_type_t<M, N>}}. | ||
| + | |||
| + | ===Parameters=== | ||
{{par begin}} | {{par begin}} | ||
{{par|m, n|integer values}} | {{par|m, n|integer values}} | ||
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If either {{c|m}} or {{c|n}} is zero, returns zero. Otherwise, returns the least common multiple of {{c|{{!}}m{{!}}}} and {{c|{{!}}n{{!}}}}. | If either {{c|m}} or {{c|n}} is zero, returns zero. Otherwise, returns the least common multiple of {{c|{{!}}m{{!}}}} and {{c|{{!}}n{{!}}}}. | ||
| − | + | ===Exceptions=== | |
| − | + | ||
| − | + | ||
| − | + | ||
| − | + | ||
| − | === Exceptions === | + | |
Throws no exceptions. | Throws no exceptions. | ||
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{{feature test macro|__cpp_lib_gcd_lcm|{{lc|std::gcd}}, {{tt|std::lcm}}|value=201606L|std=C++17}} | {{feature test macro|__cpp_lib_gcd_lcm|{{lc|std::gcd}}, {{tt|std::lcm}}|value=201606L|std=C++17}} | ||
| − | === Example === | + | ===Example=== |
{{example|code= | {{example|code= | ||
#include <iostream> | #include <iostream> | ||
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#define OUT(...) std::cout << #__VA_ARGS__ << " = " << __VA_ARGS__ << '\n' | #define OUT(...) std::cout << #__VA_ARGS__ << " = " << __VA_ARGS__ << '\n' | ||
| − | constexpr auto lcm(auto x, auto | + | constexpr auto lcm(auto x, auto... xs) |
{ | { | ||
| − | return std::lcm(x, | + | return ((x = std::lcm(x, xs)), ...); |
| − | + | ||
| − | + | ||
| − | + | ||
| − | + | ||
| − | + | ||
} | } | ||
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static_assert(225 == std::lcm(45, 75)); | static_assert(225 == std::lcm(45, 75)); | ||
| − | OUT(lcm(2*3, 3*4, 4*5)); | + | static_assert(std::lcm( 6, 10) == 30); |
| − | OUT(lcm(2*3*4, 3*4*5, 4*5*6)); | + | static_assert(std::lcm( 6, -10) == 30); |
| − | OUT(lcm(2*3*4, 3*4*5, 4*5*6, 5*6*7)); | + | 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)); | ||
} | } | ||
|output= | |output= | ||
| − | lcm(2*3, 3*4, 4*5) = 60 | + | 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) = 120 |
| − | lcm(2*3*4, 3*4*5, 4*5*6, 5*6*7) = 840 | + | lcm(2 * 3 * 4, 3 * 4 * 5, 4 * 5 * 6, 5 * 6 * 7) = 840 |
}} | }} | ||
| − | === See also === | + | ===See also=== |
{{dsc begin}} | {{dsc begin}} | ||
{{dsc inc|cpp/numeric/dsc gcd}} | {{dsc inc|cpp/numeric/dsc gcd}} | ||
| − | {{dsc end }} | + | {{dsc end}} |
{{langlinks|de|es|ja|ru|zh}} | {{langlinks|de|es|ja|ru|zh}} | ||
Latest revision as of 06:31, 14 November 2023
| 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.
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>.
Contents |
[edit] Parameters
| m, n | - | integer values |
[edit] Return value
If either m or n is zero, returns zero. Otherwise, returns the least common multiple 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
Run this code
#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)); }
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
[edit] See also
| (C++17) |
computes the greatest common divisor of two integers (function template) |
