1 
2 #ifndef BOOST_MPL_AUX_SINGLE_ELEMENT_ITER_HPP_INCLUDED
3 #define BOOST_MPL_AUX_SINGLE_ELEMENT_ITER_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/iterator_tags.hpp>
18 #include <boost/mpl/advance_fwd.hpp>
19 #include <boost/mpl/distance_fwd.hpp>
20 #include <boost/mpl/next_prior.hpp>
21 #include <boost/mpl/deref.hpp>
22 #include <boost/mpl/int.hpp>
23 #include <boost/mpl/aux_/nttp_decl.hpp>
24 #include <boost/mpl/aux_/value_wknd.hpp>
25 #include <boost/mpl/aux_/config/ctps.hpp>
26 
27 namespace boost { namespace mpl {
28 
29 #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
30 
31 namespace aux {
32 
33 template< typename T, BOOST_MPL_AUX_NTTP_DECL(int, is_last_) >
34 struct sel_iter;
35 
36 template< typename T >
37 struct sel_iter<T,0>
38 {
39     typedef random_access_iterator_tag category;
40     typedef sel_iter<T,1> next;
41     typedef T type;
42 };
43 
44 template< typename T >
45 struct sel_iter<T,1>
46 {
47     typedef random_access_iterator_tag category;
48     typedef sel_iter<T,0> prior;
49 };
50 
51 } // namespace aux
52 
53 template< typename T, BOOST_MPL_AUX_NTTP_DECL(int, is_last_), typename Distance >
54 struct advance< aux::sel_iter<T,is_last_>,Distance>
55 {
56     typedef aux::sel_iter<
57           T
58         , ( is_last_ + BOOST_MPL_AUX_NESTED_VALUE_WKND(int, Distance) )
59         > type;
60 };
61 
62 template<
63       typename T
64     , BOOST_MPL_AUX_NTTP_DECL(int, l1)
65     , BOOST_MPL_AUX_NTTP_DECL(int, l2)
66     >
67 struct distance< aux::sel_iter<T,l1>, aux::sel_iter<T,l2> >
68     : int_<( l2 - l1 )>
69 {
70 };
71 
72 #else
73 
74 namespace aux {
75 
76 struct sel_iter_tag;
77 
78 template< typename T, BOOST_MPL_AUX_NTTP_DECL(int, is_last_) >
79 struct sel_iter
80 {
81     enum { pos_ = is_last_ };
82     typedef aux::sel_iter_tag tag;
83     typedef random_access_iterator_tag category;
84 
85     typedef sel_iter<T,(is_last_ + 1)> next;
86     typedef sel_iter<T,(is_last_ - 1)> prior;
87     typedef T type;
88 };
89 
90 } // namespace aux
91 
92 template<> struct advance_impl<aux::sel_iter_tag>
93 {
94     template< typename Iterator, typename N > struct apply
95     {
96         enum { pos_ = Iterator::pos_, n_ = N::value };
97         typedef aux::sel_iter<
98               typename Iterator::type
99             , (pos_ + n_)
100             > type;
101     };
102 };
103 
104 template<> struct distance_impl<aux::sel_iter_tag>
105 {
106     template< typename Iter1, typename Iter2 > struct apply
107     {
108         enum { pos1_ = Iter1::pos_, pos2_ = Iter2::pos_ };
109         typedef int_<( pos2_ - pos1_ )> type;
110         BOOST_STATIC_CONSTANT(int, value = ( pos2_ - pos1_ ));
111     };
112 };
113 
114 #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
115 
116 }}
117 
118 #endif // BOOST_MPL_AUX_SINGLE_ELEMENT_ITER_HPP_INCLUDED
119