std::is_const
From cppreference.com
| Defined in header
<type_traits>
|
||
| template< class T >
struct is_const; |
(since C++11) | |
If T is a const-qualified type (that is, const, or const volatile), provides the member constant value equal true. For any other type, value is false.
Contents |
[edit] Template parameters
| T | - | a type to check |
[edit] Helper variable template
| template< class T >
constexpr bool is_const_v = is_const<T>::value; |
(since C++17) | |
Inherited from std::integral_constant
Member constants
| value
[static]
|
true if T is a const-qualified type , 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_const : std::false_type {}; template<class T> struct is_const<const T> : std::true_type {}; |
[edit] Example
Run this code
#include <iostream> #include <type_traits> int main() { std::cout << std::boolalpha; std::cout << std::is_const<int>::value << '\n'; std::cout << std::is_const<const int>::value << '\n'; }
Output:
false true
[edit] See also
| (C++11)
|
checks if a type is volatile-qualified (class template) |
| (library fundamentals TS)
|
variable template alias of std::is_const::value (variable template) |
| (C++17)
|
obtains a reference to const to its argument (function template) |