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

   1 [/
   2   Copyright (c) 2014 Agustin Berge
   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_final is_final]
   9    template <class T>
  10    struct is_final : public __tof {};
  11
  12 __inherit If T is a (possibly cv-qualified) class type declared with the final
  13 specifier type then inherits from __true_type, otherwise inherits from __false_type.
  14 Currently requires some kind of compiler support.
  15
  16 __std_ref 9p3.
  17
  18 __compat Without (some as yet unspecified) help from the compiler, we cannot detect
  19 class types declared with the final specifier using only standard C++,
  20 as a result this type will never inherit from __true_type, unless the user explicitly
  21 specializes the template for their user-defined final class types, or unless the compiler
  22 supplies some unspecified intrinsic that implements this functionality.
  23 Currently (June 2015) compilers more recent than GCC-4.7, Oracle-12.4, and Clang
  24 have the necessary compiler __intrinsics to ensure that this
  25 trait "just works".  You may also test to see if the necessary __intrinsics are available
  26 by checking to see if the macro `BOOST_IS_FINAL` is defined.
  27
  28 __header ` #include <boost/type_traits/is_final.hpp>` or ` #include <boost/type_traits.hpp>`
  29
  30 __examples
  31
  32 Given `struct my_final final {};` then:
  33
  34 [:`is_final<my_final>` inherits from `__true_type`.]
  35
  36 [:`is_final<const my_final>::type` is the type `__true_type`.]
  37
  38 [:`is_final<my_final>::value` is an integral constant
  39 expression that evaluates to /true/.]
  40
  41 [:`is_final<my_final*>::value` is an integral constant
  42 expression that evaluates to /false/.]
  43
  44 [:`is_final<T>::value_type` is the type `bool`.]
  45
  46 [endsect]
  47