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std::is_void

STD：：是[医]空隙

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

检查是否T是一种空型。提供成员常量。value等于true，如果T类型void，，，const void，，，volatile void，或const volatile void.否则，value等于false...

模板参数

T-a type to check

辅助变量模板

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

继承自STD：积分[医]常量

成员常数

value statictrue if T is the type void (possibly cv-qualified) , 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]无效：std：：is[医]相同的<void，type Name std：：Remove[医]CV<T>*类型>{}；

*。

例

二次

#include <iostream>
#include <type_traits>
 
int main() 
{
    std::cout << std::boolalpha;
    std::cout << std::is_void<void>::value << '\n';
    std::cout << std::is_void<int>::value << '\n';
}

二次

产出：

二次

true
false

二次

另见

is_array (C++11)checks if a type is an array type (class template)
is_pointer (C++11)checks if a type is a pointer type (class template)
is_enum (C++11)checks if a type is an enumeration type (class template)
is_union (C++11)checks if a type is an union type (class template)
is_class (C++11)checks if a type is a non-union class type (class template)
is_function (C++11)checks if a type is a function type (class template)
is_object (C++11)checks if a type is object type (class template)

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

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