ceph/src/boost/boost/spirit/home/x3/support/context.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2014 Joel de Guzman
   3     http://spirit.sourceforge.net/
   4
   5     Distributed under the Boost Software License, Version 1.0. (See accompanying
   6     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7 =============================================================================*/
   8 #if !defined(BOOST_SPIRIT_X3_CONTEXT_JAN_4_2012_1215PM)
   9 #define BOOST_SPIRIT_X3_CONTEXT_JAN_4_2012_1215PM
  10
  11 #include <boost/spirit/home/x3/support/unused.hpp>
  12 #include <boost/mpl/identity.hpp>
  13
  14 namespace boost { namespace spirit { namespace x3
  15 {
  16     template <typename ID, typename T, typename Next = unused_type>
  17     struct context
  18     {
  19         context(T& val, Next const& next)
  20             : val(val), next(next) {}
  21
  22         T& get(mpl::identity<ID>) const
  23         {
  24             return val;
  25         }
  26
  27         template <typename ID_>
  28         decltype(auto) get(ID_ id) const
  29         {
  30             return next.get(id);
  31         }
  32
  33         T& val;
  34         Next const& next;
  35     };
  36
  37     template <typename ID, typename T>
  38     struct context<ID, T, unused_type>
  39     {
  40         context(T& val)
  41             : val(val) {}
  42
  43         context(T& val, unused_type)
  44             : val(val) {}
  45
  46         T& get(mpl::identity<ID>) const
  47         {
  48             return val;
  49         }
  50
  51         template <typename ID_>
  52         unused_type get(ID_) const
  53         {
  54             return {};
  55         }
  56
  57         T& val;
  58     };
  59
  60     template <typename Tag, typename Context>
  61     inline decltype(auto) get(Context const& context)
  62     {
  63         return context.get(mpl::identity<Tag>());
  64     }
  65
  66     template <typename ID, typename T, typename Next>
  67     inline context<ID, T, Next> make_context(T& val, Next const& next)
  68     {
  69         return { val, next };
  70     }
  71
  72     template <typename ID, typename T>
  73     inline context<ID, T> make_context(T& val)
  74     {
  75         return { val };
  76     }
  77
  78     namespace detail
  79     {
  80         template <typename ID, typename T, typename Next, typename FoundVal>
  81         inline Next const&
  82         make_unique_context(T& /* val */, Next const& next, FoundVal&)
  83         {
  84             return next;
  85         }
  86
  87         template <typename ID, typename T, typename Next>
  88         inline context<ID, T, Next>
  89         make_unique_context(T& val, Next const& next, unused_type)
  90         {
  91             return { val, next };
  92         }
  93     }
  94
  95     template <typename ID, typename T, typename Next>
  96     inline auto
  97     make_unique_context(T& val, Next const& next)
  98     {
  99         return detail::make_unique_context<ID>(val, next, x3::get<ID>(next));
 100     }
 101 }}}
 102
 103 #endif