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std::is_void

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

Checks whether T is a void type. Provides the member constant value that is equal to true, if T is the type void, const void, volatile void, or const volatile void. Otherwise, value is equal to false.

The behavior of a program that adds specializations for is_void or is_void_v (since C++17) is undefined.

Template parameters

T - a type to check

Helper variable template

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

Inherited from std::integral_constant

Member constants

value
[static]
 true if T is the type void (possibly cv-qualified), false otherwise
(public static member constant)

Member functions

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

Member types

Type Definition
value_type bool
type std::integral_constant<bool, value>

Possible implementation

template<class T>
struct is_void : std::is_same<void, typename std::remove_cv<T>::type> {};

Example

#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';
}

Output:

true
false

See also

(C++11)
 checks if a type is an array type
(class template)
(C++11)
 checks if a type is a pointer type
(class template)
(C++11)
 checks if a type is an enumeration type
(class template)
(C++11)
 checks if a type is a union type
(class template)
(C++11)
 checks if a type is a non-union class type
(class template)
(C++11)
 checks if a type is a function type
(class template)
(C++11)
 checks if a type is an object type
(class template)

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