std::piecewise_construct_t
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| 在头文件 <utility> 中定义
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| struct piecewise_construct_t { }; |
（C++11 起） | |
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.
[编辑] 示例
#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); }
输出：
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
[编辑] 另请参阅
| （C++11） |
piecewise_construct_t类型的对象使用，以消除歧义分段施工的功能 原文： an object of type piecewise_construct_t used to disambiguate functions for piecewise construction （常量） |
