ceph/src/boost/libs/spirit/include/boost/spirit/home/x3/support/subcontext.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2014 Joel de Guzman
   3     Copyright (c) 2013 Agustín Bergé
   4     http://spirit.sourceforge.net/
   5
   6     Distributed under the Boost Software License, Version 1.0. (See accompanying
   7     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   8 =============================================================================*/
   9 #if !defined(BOOST_SPIRIT_X3_SUBCONTEXT_APR_15_2013_0840AM)
  10 #define BOOST_SPIRIT_X3_SUBCONTEXT_APR_15_2013_0840AM
  11
  12 #include <boost/fusion/support/pair.hpp>
  13 #include <boost/spirit/home/x3/support/context.hpp>
  14 #include <boost/spirit/home/x3/support/unused.hpp>
  15
  16 namespace boost { namespace spirit { namespace x3
  17 {
  18     template <typename... T>
  19     struct subcontext;
  20
  21     template <>
  22     struct subcontext<>
  23     {
  24         template <typename Context>
  25         subcontext(Context const& /*context*/)
  26         {}
  27
  28         template <typename ID_>
  29         unused_type
  30         get(ID_) const
  31         {
  32             return unused;
  33         }
  34     };
  35
  36     template <typename T>
  37     struct subcontext<T>
  38       : context<typename T::first_type, typename T::second_type>
  39     {
  40         typedef context<
  41             typename T::first_type, typename T::second_type
  42         > context_type;
  43
  44         template <typename Context>
  45         subcontext(Context const& context)
  46           : context_type(x3::get<typename T::first_type>(context))
  47         {}
  48
  49         using context_type::get;
  50     };
  51
  52     template <typename T, typename... Tail>
  53     struct subcontext<T, Tail...>
  54       : subcontext<Tail...>
  55       , context<
  56             typename T::first_type, typename T::second_type
  57           , subcontext<Tail...>
  58         >
  59     {
  60         typedef subcontext<Tail...> base_type;
  61         typedef context<
  62             typename T::first_type, typename T::second_type
  63           , base_type
  64         > context_type;
  65
  66         template <typename Context>
  67         subcontext(Context const& context)
  68           : base_type(context)
  69           , context_type(
  70                 x3::get<typename T::first_type>(context)
  71               , *static_cast<base_type*>(this))
  72         {}
  73
  74         using context_type::get;
  75     };
  76
  77 }}}
  78
  79 #endif