Boost
C++ Libraries
...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Boost
C++ Libraries
...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 Base, class Derived>
struct is_base_of : public true_type-or-false_type {};
Inherits: If Base is base class of type Derived or if both types are the same class type then inherits from true_type, otherwise inherits from false_type.
This template will detect non-public base classes, and ambiguous base classes. It also detects indirect base classes - which is to say is_base_of<B, D> inherits from true_type if B is located anywhere in the inheritance tree of D.
Note that is_base_of<X,X> will inherit from true_type
if X is a class type. This is a change in behaviour from Boost-1.39.0 in
order to track the emerging C++0x standard.
Types Base and Derived must not be incomplete types.
C++ Standard Reference: 10.
Header: #include
<boost/type_traits/is_base_of.hpp>
or #include <boost/type_traits.hpp>
Compiler Compatibility: All current compilers are supported by this trait.
Examples:
Given:
class Base{}; class Derived : public Base{};
is_base_of<Base, Derived>inherits fromtrue_type.
is_base_of<Base, Derived>::typeis the typetrue_type.
is_base_of<Base, Derived>::valueis an integral constant expression that evaluates to true.
is_base_of<Base, Base>::valueis an integral constant expression that evaluates to true: a class is regarded as it's own base.
is_base_of<T, T>::value_typeis the typebool.