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1 | // Copyright David Abrahams 2005. Distributed under the Boost |
2 | // Software License, Version 1.0. (See accompanying | |
3 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
4 | #ifndef BOOST_PARAMETER_BINDING_DWA200558_HPP | |
5 | # define BOOST_PARAMETER_BINDING_DWA200558_HPP | |
6 | ||
7 | # include <boost/mpl/apply.hpp> | |
8 | # include <boost/mpl/assert.hpp> | |
9 | # include <boost/mpl/and.hpp> | |
10 | # include <boost/parameter/aux_/result_of0.hpp> | |
11 | # include <boost/parameter/aux_/void.hpp> | |
12 | # include <boost/type_traits/is_same.hpp> | |
13 | ||
14 | namespace boost { namespace parameter { | |
15 | ||
16 | // A metafunction that, given an argument pack, returns the type of | |
17 | // the parameter identified by the given keyword. If no such | |
18 | // parameter has been specified, returns Default | |
19 | ||
20 | # if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564)) | |
21 | template <class Parameters, class Keyword, class Default> | |
22 | struct binding0 | |
23 | { | |
24 | typedef typename mpl::apply_wrap3< | |
25 | typename Parameters::binding,Keyword,Default,mpl::true_ | |
26 | >::type type; | |
27 | ||
28 | BOOST_MPL_ASSERT_NOT(( | |
29 | mpl::and_< | |
30 | is_same<Default, void_> | |
31 | , is_same<type, void_> | |
32 | > | |
33 | )); | |
34 | }; | |
35 | # endif | |
36 | ||
37 | template <class Parameters, class Keyword, class Default = void_> | |
38 | struct binding | |
39 | { | |
40 | # if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564)) | |
41 | typedef typename mpl::eval_if< | |
42 | mpl::is_placeholder<Parameters> | |
43 | , mpl::identity<int> | |
44 | , binding0<Parameters,Keyword,Default> | |
45 | >::type type; | |
46 | # else | |
47 | typedef typename mpl::apply_wrap3< | |
48 | typename Parameters::binding,Keyword,Default,mpl::true_ | |
49 | >::type type; | |
50 | ||
51 | BOOST_MPL_ASSERT_NOT(( | |
52 | mpl::and_< | |
53 | is_same<Default, void_> | |
54 | , is_same<type, void_> | |
55 | > | |
56 | )); | |
57 | # endif | |
58 | ||
59 | BOOST_MPL_AUX_LAMBDA_SUPPORT(3,binding,(Parameters,Keyword,Default)) | |
60 | }; | |
61 | ||
62 | // A metafunction that, given an argument pack, returns the type of | |
63 | // the parameter identified by the given keyword. If no such | |
64 | // parameter has been specified, returns the type returned by invoking | |
65 | // DefaultFn | |
66 | template <class Parameters, class Keyword, class DefaultFn> | |
67 | struct lazy_binding | |
68 | { | |
69 | typedef typename mpl::apply_wrap3< | |
70 | typename Parameters::binding | |
71 | , Keyword | |
72 | , typename aux::result_of0<DefaultFn>::type | |
73 | , mpl::true_ | |
74 | >::type type; | |
75 | }; | |
76 | ||
77 | ||
78 | }} // namespace boost::parameter | |
79 | ||
80 | #endif // BOOST_PARAMETER_BINDING_DWA200558_HPP |