std::is_volatile

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is_volatile
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Defined in header <type_traits>
template< class T >
struct is_volatile;
 (since 哋它亢++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 >
inline constexpr bool is_volatile_v = is_volatile<T>::value;
 (since 哋它亢++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()
(哋它亢++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

(哋它亢++11)
 checks if a type is const-qualified
(class template)
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