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### is_unsigned

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

Inherits: If T is an unsigned integer type or an enumerated type with an underlying unsigned integer type, then inherits from true_type, otherwise inherits from false_type.

C++ Standard Reference: 3.9.1, 7.2.

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

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

Examples:

> `is_unsigned<unsigned int>` inherits from `true_type`.

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

> `is_unsigned<int>::value` is an integral constant expression that evaluates to false.

> `is_unsigned<myclass>::value` is an integral constant expression that evaluates to false.

> `is_unsigned<char>::value` is an integral constant expression whose value depends upon the signedness of type `char`.

> `is_unsigned<unsigned long long>::value` is an integral constant expression that evaluates to true.

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