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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 #ifndef BOOST_SPIRIT_X3_NONTERMINAL_DETAIL_TRANSFORM_ATTRIBUTE_HPP
9 #define BOOST_SPIRIT_X3_NONTERMINAL_DETAIL_TRANSFORM_ATTRIBUTE_HPP
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 
preboost::spirit::x3::default_transform_attribute26         static Transformed pre(Exposed&) { return Transformed(); }
27 
postboost::spirit::x3::default_transform_attribute28         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;
preboost::spirit::x3::default_transform_attribute39         static Attribute& pre(Attribute& val) { return val; }
postboost::spirit::x3::default_transform_attribute40         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;
preboost::spirit::x3::transform_attribute53         static unused_type pre(unused_type) { return unused; }
postboost::spirit::x3::transform_attribute54         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
93