std::is_void(3) | C++ Standard Libary | std::is_void(3) |
NAME¶
std::is_void - std::is_void
Synopsis¶
Defined in header <type_traits>
template< class T > (since C++11)
struct is_void;
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 > (since C++17)
inline constexpr bool is_void_v = is_void<T>::value;
Inherited from std::integral_constant
Member constants¶
value true if T is the type void (possibly cv-qualified) , false
otherwise
[static] (public static member constant)
Member functions¶
operator bool converts the object to bool, returns value
(public member function)
operator() returns value
(C++14) (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
See also¶
is_array checks if a type is an array type
(C++11) (class template)
is_pointer checks if a type is a pointer type
(C++11) (class template)
is_enum checks if a type is an enumeration type
(C++11) (class template)
is_union checks if a type is an union type
(C++11) (class template)
is_class checks if a type is a non-union class type
(C++11) (class template)
is_function checks if a type is a function type
(C++11) (class template)
is_object checks if a type is an object type
(C++11) (class template)
2022.07.31 | http://cppreference.com |