std::piecewise_construct
STD：分段[医]构造
| constexpr piecewise_construct_t piecewise_construct = std::piecewise_construct_t( | | (since C++11) (until C++17) |
|---|---|---|
| inline constexpr piecewise_construct_t piecewise_construct = std::piecewise_construct_t( | | (since C++17) |
常数std::piecewise_construct是空struct标记类型的实例。std::piecewise_construct_t...
例
二次
#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
}
二次
产出：
二次
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
二次
另见
| piecewise_construct_t (C++11) | tag type used to select correct function overload for piecewise construction (class) |
|---|---|
| (constructor) | constructs new pair (public member function of std::pair) |
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