std::is_volatile

Defined in header <type_traits>

template< class T >
struct is_volatile;

(since C++11)

If T is a volatile-qualified type (that is, volatile, or const volatile), provides the member constant value equal true. For any other type, value is false.

Template parameters

a type to check

Helper variable template

template< class T >
constexpr bool is_volatile_v = is_volatile<T>::value;

(since C++17)

Inherited from std::integral_constant

Member constants

value

[static]

true if T is a volatile-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>`

Possible implementation

template<class T> struct is_volatile             : std::false_type {};
template<class T> struct is_volatile<volatile T> : std::true_type {};

Example

#include <iostream>
#include <type_traits>
  
int main() 
{
    std::cout << std::boolalpha;
    std::cout << std::is_volatile<int>::value << '\n';
    std::cout << std::is_volatile<volatile int>::value  << '\n';
}

Output:

false
true

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