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### is_volatile

    template <class T>
    struct is_volatile : public true_type-or-false_type {};

Inherits: If T is a (top level) volatile-qualified type then inherits from true_type, otherwise inherits from false_type.

C++ Standard Reference: 3.9.3.

Compiler Compatibility: All current compilers are supported by this trait.

Header: `#include <boost/type_traits/is_volatile.hpp>` or `#include <boost/type_traits.hpp>`

Examples:

> `is_volatile<volatile int>` inherits from `true_type`.

> `is_volatile<const volatile int>::type` is the type `true_type`.

> `is_volatile<int* volatile>::value` is an integral constant expression that evaluates to true.

> `is_volatile<int volatile*>::value` is an integral constant expression that evaluates to false: the volatile qualifier is not at the top level in this case.

> `is_volatile<T>::value_type` is the type `bool`.