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1 | |
2 | #ifndef BOOST_MPL_AUX_BEGIN_END_IMPL_HPP_INCLUDED | |
3 | #define BOOST_MPL_AUX_BEGIN_END_IMPL_HPP_INCLUDED | |
4 | ||
5 | // Copyright Aleksey Gurtovoy 2000-2004 | |
6 | // | |
7 | // Distributed under the Boost Software License, Version 1.0. | |
8 | // (See accompanying file LICENSE_1_0.txt or copy at | |
9 | // http://www.boost.org/LICENSE_1_0.txt) | |
10 | // | |
11 | // See http://www.boost.org/libs/mpl for documentation. | |
12 | ||
13 | // $Id$ | |
14 | // $Date$ | |
15 | // $Revision$ | |
16 | ||
17 | #include <boost/mpl/begin_end_fwd.hpp> | |
18 | #include <boost/mpl/sequence_tag_fwd.hpp> | |
19 | #include <boost/mpl/void.hpp> | |
20 | #include <boost/mpl/eval_if.hpp> | |
21 | #include <boost/mpl/aux_/has_begin.hpp> | |
22 | #include <boost/mpl/aux_/na.hpp> | |
23 | #include <boost/mpl/aux_/traits_lambda_spec.hpp> | |
24 | #include <boost/mpl/aux_/config/eti.hpp> | |
25 | ||
26 | namespace boost { namespace mpl { | |
27 | ||
28 | ||
29 | namespace aux { | |
30 | ||
31 | template< typename Sequence > | |
32 | struct begin_type | |
33 | { | |
34 | typedef typename Sequence::begin type; | |
35 | }; | |
36 | template< typename Sequence > | |
37 | struct end_type | |
38 | { | |
39 | typedef typename Sequence::end type; | |
40 | }; | |
41 | ||
42 | } | |
43 | ||
44 | // default implementation; conrete sequences might override it by | |
45 | // specializing either the 'begin_impl/end_impl' or the primary | |
46 | // 'begin/end' templates | |
47 | ||
48 | template< typename Tag > | |
49 | struct begin_impl | |
50 | { | |
51 | template< typename Sequence > struct apply | |
52 | { | |
53 | typedef typename eval_if<aux::has_begin<Sequence, true_>, | |
54 | aux::begin_type<Sequence>, void_>::type type; | |
55 | }; | |
56 | }; | |
57 | ||
58 | template< typename Tag > | |
59 | struct end_impl | |
60 | { | |
61 | template< typename Sequence > struct apply | |
62 | { | |
63 | typedef typename eval_if<aux::has_begin<Sequence, true_>, | |
64 | aux::end_type<Sequence>, void_>::type type; | |
65 | }; | |
66 | }; | |
67 | ||
68 | // specialize 'begin_trait/end_trait' for two pre-defined tags | |
69 | ||
70 | # define AUX778076_IMPL_SPEC(name, tag, result) \ | |
71 | template<> \ | |
72 | struct name##_impl<tag> \ | |
73 | { \ | |
74 | template< typename Sequence > struct apply \ | |
75 | { \ | |
76 | typedef result type; \ | |
77 | }; \ | |
78 | }; \ | |
79 | /**/ | |
80 | ||
81 | // a sequence with nested 'begin/end' typedefs; just query them | |
82 | AUX778076_IMPL_SPEC(begin, nested_begin_end_tag, typename Sequence::begin) | |
83 | AUX778076_IMPL_SPEC(end, nested_begin_end_tag, typename Sequence::end) | |
84 | ||
85 | // if a type 'T' does not contain 'begin/end' or 'tag' members | |
86 | // and doesn't specialize either 'begin/end' or 'begin_impl/end_impl' | |
87 | // templates, then we end up here | |
88 | AUX778076_IMPL_SPEC(begin, non_sequence_tag, void_) | |
89 | AUX778076_IMPL_SPEC(end, non_sequence_tag, void_) | |
90 | AUX778076_IMPL_SPEC(begin, na, void_) | |
91 | AUX778076_IMPL_SPEC(end, na, void_) | |
92 | ||
93 | # undef AUX778076_IMPL_SPEC | |
94 | ||
95 | ||
96 | BOOST_MPL_ALGORITM_TRAITS_LAMBDA_SPEC_IMPL(1,begin_impl) | |
97 | BOOST_MPL_ALGORITM_TRAITS_LAMBDA_SPEC_IMPL(1,end_impl) | |
98 | ||
99 | }} | |
100 | ||
101 | #endif // BOOST_MPL_AUX_BEGIN_END_IMPL_HPP_INCLUDED |