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.

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)

Member types

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

[edit] Possible implementation

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

[edit] 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

[edit] See also

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 class type (but not union 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)

Language
Standard library headers
Concepts
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)

Type support (basic types, RTTI, type traits)
Dynamic memory management
Error handling
Program utilities
Variadic functions
Date and time
Function objects
initializer_list (C++11)
bitset
hash (C++11)
Relational operators
rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
Pairs and tuples
pair
tuple (C++11)
piecewise_construct_t (C++11)
piecewise_construct (C++11)
Swap, forward and move
swap
forward (C++11)
move (C++11)
move_if_noexcept (C++11)
declval (C++11)