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 > 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 an 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 object type (class template) |
std::experimental::is_void_v
(library fundamentals TS) | variable template alias of std::is_void::value (variable template) |
Please login to continue.