Difference between revisions of "cpp/numeric/lcm"
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Andreas Krug (Talk | contribs) m ({{c}}, headers sorted, fmt) |
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{{cpp/numeric/navbar}} | {{cpp/numeric/navbar}} | ||
{{dcl begin}} | {{dcl begin}} | ||
| − | {{dcl header | numeric }} | + | {{dcl header|numeric}} |
| − | {{dcl | since=c++17 | | + | {{dcl|since=c++17| |
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 ); | ||
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{{dcl end}} | {{dcl end}} | ||
| − | Computes the least common multiple of the integers {{ | + | Computes the least common multiple of the integers {{c|m}} and {{c|n}}. |
=== Parameters === | === Parameters === | ||
{{par begin}} | {{par begin}} | ||
| − | {{par | m, n | integer values}} | + | {{par|m, n|integer values}} |
{{par end}} | {{par end}} | ||
===Return value=== | ===Return value=== | ||
| − | If either {{ | + | If either {{c|m}} or {{c|n}} is zero, returns zero. Otherwise, returns the least common multiple of {{c|{{!}}m{{!}}}} and {{c|{{!}}n{{!}}}}. |
=== Remarks === | === Remarks === | ||
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. | 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 {{ | + | 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>}}. |
=== Exceptions === | === Exceptions === | ||
| Line 32: | Line 32: | ||
=== Example === | === Example === | ||
{{example|code= | {{example|code= | ||
| − | |||
#include <iostream> | #include <iostream> | ||
| + | #include <numeric> | ||
#define OUT(...) std::cout << #__VA_ARGS__ << " = " << __VA_ARGS__ << '\n' | #define OUT(...) std::cout << #__VA_ARGS__ << " = " << __VA_ARGS__ << '\n' | ||
| − | constexpr auto lcm(auto x, auto y) { | + | constexpr auto lcm(auto x, auto y) |
| − | return std::lcm(x,y); | + | { |
| + | return std::lcm(x, y); | ||
} | } | ||
| − | constexpr auto lcm(auto head, auto...tail) { | + | |
| + | constexpr auto lcm(auto head, auto...tail) | ||
| + | { | ||
return std::lcm(head, lcm(tail...)); | return std::lcm(head, lcm(tail...)); | ||
} | } | ||
| − | int main() { | + | int main() |
| − | constexpr int p {2 * 2 * 3}; | + | { |
| − | constexpr int q {2 * 3 * 3}; | + | constexpr int p{2 * 2 * 3}; |
| + | constexpr int q{2 * 3 * 3}; | ||
static_assert(2 * 2 * 3 * 3 == std::lcm(p, q)); | static_assert(2 * 2 * 3 * 3 == std::lcm(p, q)); | ||
static_assert(225 == std::lcm(45, 75)); | static_assert(225 == std::lcm(45, 75)); | ||
| Line 54: | Line 58: | ||
OUT(lcm(2*3*4, 3*4*5, 4*5*6, 5*6*7)); | 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, 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 | ||
| Line 62: | Line 66: | ||
=== 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}} | ||
Revision as of 09:38, 9 May 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.
Contents |
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 <iostream> #include <numeric> #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
| (C++17) |
computes the greatest common divisor of two integers (function template) |
