ceph/src/boost/libs/variant/include/boost/variant/detail/enable_recursive_fwd.hpp

   1 //-----------------------------------------------------------------------------
   2 // boost variant/detail/enable_recursive_fwd.hpp header file
   3 // See http://www.boost.org for updates, documentation, and revision history.
   4 //-----------------------------------------------------------------------------
   5 //
   6 // Copyright (c) 2003
   7 // Eric Friedman
   8 //
   9 // Distributed under the Boost Software License, Version 1.0. (See
  10 // accompanying file LICENSE_1_0.txt or copy at
  11 // http://www.boost.org/LICENSE_1_0.txt)
  12
  13 #ifndef BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_FWD_HPP
  14 #define BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_FWD_HPP
  15
  16 #include <boost/mpl/aux_/config/ctps.hpp>
  17
  18 #include <boost/mpl/bool_fwd.hpp>
  19
  20 #   include <boost/mpl/bool.hpp>
  21
  22 namespace boost {
  23 namespace detail { namespace variant {
  24
  25 ///////////////////////////////////////////////////////////////////////////////
  26 // (detail) tag recursive_flag
  27 //
  28 // Signifies that the variant should perform recursive substituion.
  29 //
  30
  31
  32 template <typename T>
  33 struct recursive_flag
  34 {
  35     typedef T type;
  36 };
  37
  38
  39 ///////////////////////////////////////////////////////////////////////////////
  40 // (detail) metafunction is_recursive_flag
  41 //
  42 // Signifies that the variant should perform recursive substituion.
  43 //
  44
  45
  46 template <typename T>
  47 struct is_recursive_flag
  48     : mpl::false_
  49 {
  50 };
  51
  52 template <typename T>
  53 struct is_recursive_flag< recursive_flag<T> >
  54     : mpl::true_
  55 {
  56 };
  57
  58
  59 ///////////////////////////////////////////////////////////////////////////////
  60 // (detail) metafunction enable_recursive
  61 //
  62 // Attempts recursive_variant_ tag substitution, wrapping with
  63 // boost::recursive_wrapper if substituion occurs w/ non-indirect result
  64 // (i.e., not a reference or pointer) *and* NoWrapper is false_.
  65 //
  66 template <
  67       typename T
  68     , typename RecursiveVariant
  69     , typename NoWrapper = mpl::false_
  70     >
  71 struct enable_recursive;
  72
  73 ///////////////////////////////////////////////////////////////////////////////
  74 // (detail) metafunction class quoted_enable_recursive
  75 //
  76 // Same behavior as enable_recursive metafunction (see above).
  77 //
  78 template <
  79       typename RecursiveVariant
  80     , typename NoWrapper = mpl::false_
  81     >
  82 struct quoted_enable_recursive;
  83
  84 }} // namespace detail::variant
  85 } // namespace boost
  86
  87 #endif // BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_FWD_HPP