std::piecewise_construct_t
Материал из cppreference.com
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| Заголовочный файл <utility>
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| struct piecewise_construct_t { }; |
(начиная с C++11) | |
std::piecewise_construct_t is an empty struct tag type used to disambiguate between different functions that take two tuple arguments.
The overloads that do not use std::piecewise_construct_t assume that each tuple argument becomes the element of a pair. The overloads that use std::piecewise_construct_t assume that each tuple argument is used to construct, piecewise, a new object of specified type, which will become the element of the pair.
[править] Пример
#include <iostream> #include <utility> #include <tuple> struct Foo { Foo(std::tuple<int, float>) { std::cout << "Constructed a Foo from a tuple\n"; } Foo(int, float) { std::cout << "Constructed a Foo from an int and a float\n"; } }; int main() { std::tuple<int, float> t(1, 3.14); std::pair<Foo, Foo> p1(t, t); std::pair<Foo, Foo> p2(std::piecewise_construct, t, t); }
Вывод:
Constructed a Foo from a tuple Constructed a Foo from a tuple Constructed a Foo from an int and a float Constructed a Foo from an int and a float
[править] См. также
| (C++11) |
Объект типа piecewise_construct_t используется для устранения неоднозначности функции для кусочно строительства Original: an object of type piecewise_construct_t used to disambiguate functions for piecewise construction The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (константа) |
