ceph/src/boost/boost/spirit/home/x3/nonterminal/detail/transform_attribute.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2014 Joel de Guzman
   3     Copyright (c) 2001-2011 Hartmut Kaiser
   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(SPIRIT_X3_DETAIL_ATTRIBUTES_APR_18_2010_0458PM)
   9 #define SPIRIT_X3_DETAIL_ATTRIBUTES_APR_18_2010_0458PM
  10
  11 #include <boost/spirit/home/x3/support/traits/transform_attribute.hpp>
  12 #include <boost/spirit/home/x3/support/traits/move_to.hpp>
  13 #include <type_traits>
  14 #include <utility>
  15
  16 ///////////////////////////////////////////////////////////////////////////////
  17 namespace boost { namespace spirit { namespace x3
  18 {
  19     struct parser_id;
  20
  21     template <typename Exposed, typename Transformed>
  22     struct default_transform_attribute
  23     {
  24         typedef Transformed type;
  25
  26         static Transformed pre(Exposed&) { return Transformed(); }
  27
  28         static void post(Exposed& val, Transformed&& attr)
  29         {
  30             traits::move_to(std::forward<Transformed>(attr), val);
  31         }
  32     };
  33
  34     // handle case where no transformation is required as the types are the same
  35     template <typename Attribute>
  36     struct default_transform_attribute<Attribute, Attribute>
  37     {
  38         typedef Attribute& type;
  39         static Attribute& pre(Attribute& val) { return val; }
  40         static void post(Attribute&, Attribute const&) {}
  41     };
  42
  43     // main specialization for x3
  44     template <typename Exposed, typename Transformed, typename Enable = void>
  45     struct transform_attribute
  46       : default_transform_attribute<Exposed, Transformed> {};
  47
  48     // unused_type needs some special handling as well
  49     template <>
  50     struct transform_attribute<unused_type, unused_type>
  51     {
  52         typedef unused_type type;
  53         static unused_type pre(unused_type) { return unused; }
  54         static void post(unused_type, unused_type) {}
  55     };
  56
  57     template <>
  58     struct transform_attribute<unused_type const, unused_type>
  59       : transform_attribute<unused_type, unused_type> {};
  60
  61     template <typename Attribute>
  62     struct transform_attribute<unused_type, Attribute>
  63       : transform_attribute<unused_type, unused_type> {};
  64
  65     template <typename Attribute>
  66     struct transform_attribute<unused_type const, Attribute>
  67       : transform_attribute<unused_type, unused_type> {};
  68
  69     template <typename Attribute>
  70     struct transform_attribute<Attribute, unused_type>
  71       : transform_attribute<unused_type, unused_type> {};
  72
  73     template <typename Attribute>
  74     struct transform_attribute<Attribute const, unused_type>
  75       : transform_attribute<unused_type, unused_type> {};
  76 }}}
  77
  78 ///////////////////////////////////////////////////////////////////////////////
  79 namespace boost { namespace spirit { namespace x3 { namespace traits
  80 {
  81     template <typename Exposed, typename Transformed>
  82     struct transform_attribute<Exposed, Transformed, x3::parser_id>
  83       : x3::transform_attribute<Exposed, Transformed>
  84     {
  85         static_assert(!std::is_reference<Exposed>::value,
  86             "Exposed cannot be a reference type");
  87         static_assert(!std::is_reference<Transformed>::value,
  88             "Transformed cannot be a reference type");
  89     };
  90 }}}}
  91
  92 #endif