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
26namespace boost { namespace mpl {
27
28
29namespace aux {
30
31template< typename Sequence >
32struct begin_type
33{
34 typedef typename Sequence::begin type;
35};
36template< typename Sequence >
37struct 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
48template< typename Tag >
49struct 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
58template< typename Tag >
59struct 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) \
71template<> \
72struct 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
82AUX778076_IMPL_SPEC(begin, nested_begin_end_tag, typename Sequence::begin)
83AUX778076_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
88AUX778076_IMPL_SPEC(begin, non_sequence_tag, void_)
89AUX778076_IMPL_SPEC(end, non_sequence_tag, void_)
90AUX778076_IMPL_SPEC(begin, na, void_)
91AUX778076_IMPL_SPEC(end, na, void_)
92
93# undef AUX778076_IMPL_SPEC
94
95
96BOOST_MPL_ALGORITM_TRAITS_LAMBDA_SPEC_IMPL(1,begin_impl)
97BOOST_MPL_ALGORITM_TRAITS_LAMBDA_SPEC_IMPL(1,end_impl)
98
99}}
100
101#endif // BOOST_MPL_AUX_BEGIN_END_IMPL_HPP_INCLUDED
102

source code of boost/boost/mpl/aux_/begin_end_impl.hpp