ceph/src/boost/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/spirit/home/x3/support/context.hpp>
  13 #include <boost/spirit/home/x3/support/unused.hpp>
  14
  15 namespace boost { namespace spirit { namespace x3
  16 {
  17     template <typename... T>
  18     struct subcontext;
  19
  20     template <>
  21     struct subcontext<>
  22     {
  23         template <typename Context>
  24         subcontext(Context const& /*context*/)
  25         {}
  26
  27         template <typename ID_>
  28         unused_type
  29         get(ID_) const
  30         {
  31             return unused;
  32         }
  33     };
  34
  35     template <typename T>
  36     struct subcontext<T>
  37       : context<typename T::first_type, typename T::second_type>
  38     {
  39         typedef context<
  40             typename T::first_type, typename T::second_type
  41         > context_type;
  42
  43         template <typename Context>
  44         subcontext(Context const& context)
  45           : context_type(x3::get<typename T::first_type>(context))
  46         {}
  47
  48         using context_type::get;
  49     };
  50
  51     template <typename T, typename... Tail>
  52     struct subcontext<T, Tail...>
  53       : subcontext<Tail...>
  54       , context<
  55             typename T::first_type, typename T::second_type
  56           , subcontext<Tail...>
  57         >
  58     {
  59         typedef subcontext<Tail...> base_type;
  60         typedef context<
  61             typename T::first_type, typename T::second_type
  62           , base_type
  63         > context_type;
  64
  65         template <typename Context>
  66         subcontext(Context const& context)
  67           : base_type(context)
  68           , context_type(
  69                 x3::get<typename T::first_type>(context)
  70               , *static_cast<base_type*>(this))
  71         {}
  72
  73         using context_type::get;
  74     };
  75
  76 }}}
  77
  78 #endif