ceph/src/boost/libs/type_traits/doc/is_base_of.qbk

   1 [/
   2   Copyright 2007 John Maddock.
   3   Distributed under the Boost Software License, Version 1.0.
   4   (See accompanying file LICENSE_1_0.txt or copy at
   5   http://www.boost.org/LICENSE_1_0.txt).
   6 ]
   7
   8 [section:is_base_of is_base_of]
   9
  10    template <class Base, class Derived>
  11    struct is_base_of : public __tof {};
  12
  13 __inherit If Base is base class of type Derived or if both types are the same
  14 class type then inherits from __true_type,
  15 otherwise inherits from __false_type.
  16
  17 This template will detect non-public base classes, and ambiguous base classes.
  18 It also detects indirect base classes - which is to say __is_base_of<B, D> inherits
  19 from __true_type if B is located anywhere in the inheritance tree of D.
  20
  21 Note that `is_base_of<X,X>` will inherit from __true_type if X is a class type.
  22 This is a change in behaviour
  23 from Boost-1.39.0 in order to track the emerging C++0x standard.
  24
  25 Types `Base` and `Derived` must not be incomplete types.
  26
  27 __std_ref 10.
  28
  29 __header ` #include <boost/type_traits/is_base_of.hpp>` or ` #include <boost/type_traits.hpp>`
  30
  31 [all_compilers]
  32
  33 __examples
  34
  35 [:Given: ` class Base{}; class Derived : public Base{};` ]
  36
  37 [:`is_base_of<Base, Derived>` inherits from `__true_type`.]
  38
  39 [:`is_base_of<Base, Derived>::type` is the type `__true_type`.]
  40
  41 [:`is_base_of<Base, Derived>::value` is an integral constant
  42 expression that evaluates to /true/.]
  43
  44 [:`is_base_of<Base, Base>::value` is an integral constant
  45 expression that evaluates to /true/: a class is regarded as it's own base.]
  46
  47 [:`is_base_of<T, T>::value_type` is the type `bool`.]
  48
  49 [endsect]
  50
  51
  52