std::is_void
From cppreference.com
Defined in header <type_traits> | ||
template<class T > struct is_void; | (since C++11) | |
std::is_void is a UnaryTypeTrait.
Checks whether T is a void type. Provides the member constant value that is equal to true, if T is the type void, constvoid, volatilevoid, or constvolatilevoid. Otherwise, value is equal to false.
If the program adds specializations for std::is_void or std::is_void_v, the behavior is undefined.
Contents |
[edit]Template parameters
| T | - | a type to check |
[edit]Helper variable template
template<class T > constexprbool 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> |
[edit]Possible implementation
template<class T>struct is_void :std::is_same<void, typenamestd::remove_cv<T>::type>{}; |
[edit]Example
Run this code
#include <type_traits> void foo(); static_assert ( std::is_void_v<void>==true and std::is_void_v<constvoid>==true and std::is_void_v<volatilevoid>==true and std::is_void_v<void*>==false and std::is_void_v<int>==false and std::is_void_v<decltype(foo)>==false and std::is_void_v<std::is_void<void>>==false); int main(){}
[edit]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) |
