std::is_const
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                    | 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 Tis 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) | 


