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.

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

Run this code

#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

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 an object type (class template)

Language
Standard Library Headers
Freestanding and hosted implementations
Named requirements
Language support library
Concepts library (C++20)
Diagnostics library
Utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Filesystem library (C++17)
Technical Specifications