std::is_volatile

 

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Defined in header <type_traits>
template< class T > struct is_volatile;		(since C++11)

std::is_volatile is a UnaryTypeTrait.

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

If the program adds specializations for std::is_volatile or std::is_volatile_v, the behavior is undefined.

Template parameters

T

-

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

Run this code

#include <type_traits>
#include <valarray>
 
static_assert(!std::is_volatile_v<int>);
static_assert(std::is_volatile_v<volatile int>);
static_assert(std::is_volatile_v<volatile const int>);
static_assert(std::is_volatile_v<volatile std::valarray<float>>);
static_assert(!std::is_volatile_v<std::valarray<volatile float>>);
 
int main() {}

See also

is_const (C++11)

checks if a type is const-qualified (class template)