]>
Commit | Line | Data |
---|---|---|
7c673cae FG |
1 | |
2 | // (C) Copyright Edward Diener 2011,2012,2013 | |
3 | // Use, modification and distribution are subject to the Boost Software License, | |
4 | // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at | |
5 | // http://www.boost.org/LICENSE_1_0.txt). | |
6 | ||
7 | #if !defined(BOOST_TTI_HAS_TYPE_HPP) | |
8 | #define BOOST_TTI_HAS_TYPE_HPP | |
9 | ||
10 | #include <boost/config.hpp> | |
11 | #include <boost/preprocessor/cat.hpp> | |
12 | #include <boost/tti/gen/has_type_gen.hpp> | |
13 | #include <boost/tti/gen/namespace_gen.hpp> | |
14 | #include <boost/tti/detail/dtype.hpp> | |
15 | #include <boost/tti/detail/ddeftype.hpp> | |
16 | ||
17 | /* | |
18 | ||
19 | The succeeding comments in this file are in doxygen format. | |
20 | ||
21 | */ | |
22 | ||
23 | /** \file | |
24 | */ | |
25 | ||
26 | /** | |
27 | ||
28 | BOOST_TTI_TRAIT_HAS_TYPE is a macro which expands to a metafunction. | |
29 | The metafunction tests whether an inner type with a particular name exists | |
30 | and, optionally, whether a lambda expression invoked with the inner type | |
31 | is true or not. | |
32 | ||
33 | trait = the name of the metafunction within the tti namespace. | |
34 | ||
35 | name = the name of the inner type. | |
36 | ||
37 | generates a metafunction called "trait" where 'trait' is the macro parameter. | |
38 | ||
39 | template<class BOOST_TTI_TP_T,class BOOST_TTI_TP_U> | |
40 | struct trait | |
41 | { | |
42 | static const value = unspecified; | |
43 | typedef mpl::bool_<true-or-false> type; | |
44 | }; | |
45 | ||
46 | The metafunction types and return: | |
47 | ||
48 | BOOST_TTI_TP_T = the enclosing type in which to look for our 'name'. | |
49 | ||
50 | BOOST_TTI_TP_U = (optional) An optional template parameter, defaulting to a marker type. | |
51 | If specified it is an MPL lambda expression which is invoked | |
52 | with the inner type found and must return a constant boolean | |
53 | value. | |
54 | ||
55 | returns = 'value' depends on whether or not the optional BOOST_TTI_TP_U is specified. | |
56 | ||
57 | If BOOST_TTI_TP_U is not specified, then 'value' is true if the 'name' type | |
58 | exists within the enclosing type BOOST_TTI_TP_T; otherwise 'value' is false. | |
59 | ||
60 | If BOOST_TTI_TP_U is specified , then 'value' is true if the 'name' type exists | |
61 | within the enclosing type BOOST_TTI_TP_T and the lambda expression as specified | |
62 | by BOOST_TTI_TP_U, invoked by passing the actual inner type of 'name', returns | |
63 | a 'value' of true; otherwise 'value' is false. | |
64 | ||
65 | The action taken with BOOST_TTI_TP_U occurs only when the 'name' type exists | |
66 | within the enclosing type BOOST_TTI_TP_T. | |
67 | ||
68 | Example usage: | |
69 | ||
70 | BOOST_TTI_TRAIT_HAS_TYPE(LookFor,MyType) generates the metafunction LookFor in the current scope | |
71 | to look for an inner type called MyType. | |
72 | ||
73 | LookFor<EnclosingType>::value is true if MyType is an inner type of EnclosingType, otherwise false. | |
74 | ||
75 | LookFor<EnclosingType,ALambdaExpression>::value is true if MyType is an inner type of EnclosingType | |
76 | and invoking ALambdaExpression with the inner type returns a value of true, otherwise false. | |
77 | ||
78 | A popular use of the optional MPL lambda expression is to check whether the type found is the same | |
79 | as another type, when the type found is a typedef. In that case our example would be: | |
80 | ||
81 | LookFor<EnclosingType,boost::is_same<_,SomeOtherType> >::value is true if MyType is an inner type | |
82 | of EnclosingType and is the same type as SomeOtherType. | |
83 | ||
84 | */ | |
85 | #define BOOST_TTI_TRAIT_HAS_TYPE(trait,name) \ | |
86 | BOOST_TTI_DETAIL_TRAIT_HAS_TYPE(trait,name) \ | |
87 | template \ | |
88 | < \ | |
89 | class BOOST_TTI_TP_T, \ | |
90 | class BOOST_TTI_TP_U = BOOST_TTI_NAMESPACE::detail::deftype \ | |
91 | > \ | |
92 | struct trait \ | |
93 | { \ | |
94 | typedef typename \ | |
95 | BOOST_PP_CAT(trait,_detail_type)<BOOST_TTI_TP_T,BOOST_TTI_TP_U>::type type; \ | |
96 | BOOST_STATIC_CONSTANT(bool,value=type::value); \ | |
97 | }; \ | |
98 | /**/ | |
99 | ||
100 | /** | |
101 | ||
102 | BOOST_TTI_HAS_TYPE is a macro which expands to a metafunction. | |
103 | The metafunction tests whether an inner type with a particular name exists | |
104 | and, optionally, whether a lambda expression invoked with the inner type | |
105 | is true or not. | |
106 | ||
107 | name = the name of the inner type. | |
108 | ||
109 | generates a metafunction called "has_type_'name'" where 'name' is the macro parameter. | |
110 | ||
111 | template<class BOOST_TTI_TP_T,class BOOST_TTI_TP_U> | |
112 | struct has_type_'name' | |
113 | { | |
114 | static const value = unspecified; | |
115 | typedef mpl::bool_<true-or-false> type; | |
116 | }; | |
117 | ||
118 | The metafunction types and return: | |
119 | ||
120 | BOOST_TTI_TP_T = the enclosing type in which to look for our 'name'. | |
121 | ||
122 | BOOST_TTI_TP_U = (optional) An optional template parameter, defaulting to a marker type. | |
123 | If specified it is an MPL lambda expression which is invoked | |
124 | with the inner type found and must return a constant boolean | |
125 | value. | |
126 | ||
127 | returns = 'value' depends on whether or not the optional BOOST_TTI_TP_U is specified. | |
128 | ||
129 | If BOOST_TTI_TP_U is not specified, then 'value' is true if the 'name' type | |
130 | exists within the enclosing type BOOST_TTI_TP_T; otherwise 'value' is false. | |
131 | ||
132 | If BOOST_TTI_TP_U is specified , then 'value' is true if the 'name' type exists | |
133 | within the enclosing type BOOST_TTI_TP_T and the lambda expression as specified | |
134 | by BOOST_TTI_TP_U, invoked by passing the actual inner type of 'name', returns | |
135 | a 'value' of true; otherwise 'value' is false. | |
136 | ||
137 | The action taken with BOOST_TTI_TP_U occurs only when the 'name' type exists | |
138 | within the enclosing type BOOST_TTI_TP_T. | |
139 | ||
140 | Example usage: | |
141 | ||
142 | BOOST_TTI_HAS_TYPE(MyType) generates the metafunction has_type_MyType in the current scope | |
143 | to look for an inner type called MyType. | |
144 | ||
145 | has_type_MyType<EnclosingType>::value is true if MyType is an inner type of EnclosingType, otherwise false. | |
146 | ||
147 | has_type_MyType<EnclosingType,ALambdaExpression>::value is true if MyType is an inner type of EnclosingType | |
148 | and invoking ALambdaExpression with the inner type returns a value of true, otherwise false. | |
149 | ||
150 | A popular use of the optional MPL lambda expression is to check whether the type found is the same | |
151 | as another type, when the type found is a typedef. In that case our example would be: | |
152 | ||
153 | has_type_MyType<EnclosingType,boost::is_same<_,SomeOtherType> >::value is true if MyType is an inner type | |
154 | of EnclosingType and is the same type as SomeOtherType. | |
155 | ||
156 | */ | |
157 | #define BOOST_TTI_HAS_TYPE(name) \ | |
158 | BOOST_TTI_TRAIT_HAS_TYPE \ | |
159 | ( \ | |
160 | BOOST_TTI_HAS_TYPE_GEN(name), \ | |
161 | name \ | |
162 | ) \ | |
163 | /**/ | |
164 | ||
165 | #endif // BOOST_TTI_HAS_TYPE_HPP |