std::tuple_size<std::pair>
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<tbody> </tbody>| Definido no cabeçalho <utility>
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template< class T1, class T2 > struct tuple_size<std::pair<T1, T2>>; |
(desde C++11) | |
The partial specialization of std::tuple_size for pairs provides a compile-time way to obtain the number of elements in a pair, which is always 2, using tuple-like syntax.
Members | |
value [estática] |
integral constant with value 2 (membro estático público constante) |
Exemplo
#include <iostream>
#include <utility>
#include <tuple>
template<class T>
void test(T t)
{
int a[std::tuple_size<T>::value]; // can be used at compile time
std::cout << std::tuple_size<T>::value << '\n'; // or at run time
}
int main()
{
test(std::make_tuple(1, 2, 3.14));
test(std::make_pair(1, 3.14));
}
Saída:
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