...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
template <class T>
struct is_class : public true_type-or-false_type
{};
Inherits: If T is a (possibly cv-qualified) class type then inherits from true_type, otherwise inherits from false_type.
C++ Standard Reference: 3.9.2 and 9.2.
Header: #include
<boost/type_traits/is_class.hpp>
or #include <boost/type_traits.hpp>
Compiler Compatibility: Without (some as yet unspecified) help from the compiler, we cannot distinguish between union and class types, as a result this type will erroneously inherit from true_type for union types. See also is_union. Currently (May 2005) only Visual C++ 8 has the necessary compiler intrinsics to correctly identify union types, and therefore make is_class function correctly.
Examples:
Given:
class MyClass;
then:
is_class<MyClass>
inherits fromtrue_type
.
is_class<MyClass const>::type
is the typetrue_type
.
is_class<MyClass>::value
is an integral constant expression that evaluates to true.
is_class<MyClass&>::value
is an integral constant expression that evaluates to false.
is_class<MyClass*>::value
is an integral constant expression that evaluates to false.
is_class<T>::value_type
is the typebool
.