std::is_const

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.

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

is_volatile (C++11)	checks if a type is volatile-qualified (class template)
std::experimental::is_const_v (library fundamentals TS)	variable template alias of `std::is_const::value` (variable template)

Language
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Utilities library
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rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
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move (C++11)
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