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

   1 /*=============================================================================
   2     Copyright (c) 2001-2014 Joel de Guzman
   3     Copyright (c) 2001-2012 Hartmut Kaiser
   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_MAKE_ATTRIBUTE_JAN_8_2012_0721PM)
  10 #define BOOST_SPIRIT_X3_MAKE_ATTRIBUTE_JAN_8_2012_0721PM
  11
  12 #include <boost/mpl/if.hpp>
  13 #include <boost/type_traits/remove_const.hpp>
  14 #include <boost/type_traits/add_reference.hpp>
  15 #include <boost/spirit/home/x3/support/unused.hpp>
  16
  17 namespace boost { namespace spirit { namespace x3 { namespace traits
  18 {
  19     template <typename Attribute>
  20     struct make_attribute_base
  21     {
  22         static Attribute call(unused_type)
  23         {
  24              // synthesize the attribute/parameter
  25             return Attribute();
  26         }
  27
  28         template <typename T>
  29         static T& call(T& value)
  30         {
  31             return value; // just pass the one provided
  32         }
  33     };
  34
  35     template <typename Attribute, typename ActualAttribute>
  36     struct make_attribute : make_attribute_base<Attribute>
  37     {
  38         typedef ActualAttribute& type;
  39         typedef ActualAttribute value_type;
  40     };
  41
  42     template <typename Attribute>
  43     struct make_attribute<Attribute, unused_type>
  44         : make_attribute_base<Attribute>
  45     {
  46         typedef typename remove_const<Attribute>::type attribute_type;
  47         typedef attribute_type type;
  48         typedef attribute_type value_type;
  49     };
  50
  51     template <typename Attribute, typename ActualAttribute>
  52     struct make_attribute<Attribute&, ActualAttribute>
  53       : make_attribute<Attribute, ActualAttribute> {};
  54
  55     template <typename Attribute, typename ActualAttribute>
  56     struct make_attribute<Attribute const&, ActualAttribute>
  57       : make_attribute<Attribute const, ActualAttribute> {};
  58
  59     template <typename ActualAttribute>
  60     struct make_attribute<unused_type, ActualAttribute>
  61     {
  62         typedef unused_type type;
  63         typedef unused_type value_type;
  64         static unused_type call(unused_type)
  65         {
  66             return unused;
  67         }
  68     };
  69
  70     template <>
  71     struct make_attribute<unused_type, unused_type>
  72     {
  73         typedef unused_type type;
  74         typedef unused_type value_type;
  75         static unused_type call(unused_type)
  76         {
  77             return unused;
  78         }
  79     };
  80 }}}}
  81
  82 #endif