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std::is_reference

STD：：是[医]参照系

Defined in header ​​
template< class T > struct is_reference;​(since C++11)

如果T是引用类型%28 lvalue引用或rvalue引用%29，提供成员常量value平等true.对于任何其他类型，value是false...

模板参数

T-a type to check

辅助变量模板

template< class T > inline constexpr bool is_reference_v = is_reference::value;​(since C++17)

继承自STD：积分[医]常量

成员常数

value statictrue if T is a reference type , false otherwise (public static member constant)

成员函数

operator boolconverts the object to bool, returns value (public member function)
operator() (C++14)returns value (public member function)

成员类型

TypeDefinition
value_typebool
typestd::integral_constant<bool, value>

可能的实施

模板<class T>结构是[医]参考资料：std：：false[医]类型{}；模板<class T>结构是[医]参考<T&>：std：：true[医]类型{}；模板<class T>结构是[医]参考<T&>：std：：true[医]{}型；

*。

例

二次

#include <iostream>
#include <type_traits>
 
class A {};
 
int main() 
{
    std::cout << std::boolalpha;
    std::cout << std::is_reference<A>::value << '\n';
    std::cout << std::is_reference<A&>::value << '\n';
    std::cout << std::is_reference<A&&>::value << '\n';
    std::cout << std::is_reference<int>::value << '\n';
    std::cout << std::is_reference<int&>::value << '\n';
    std::cout << std::is_reference<int&&>::value << '\n';
}

二次

产出：

二次

false
true
true
false
true
true

二次

另见

is_lvalue_reference (C++11)checks if a type is lvalue reference (class template)
is_rvalue_reference (C++11)checks if a type is rvalue reference (class template)

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http：//en.cppreference.com/w/cpp/type/is[医]参照系

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