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   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: single_element_iter.hpp 49267 2008-10-11 06:19:02Z agurtovoy $
  14 // $Date: 2008-10-11 02:19:02 -0400 (Sat, 11 Oct 2008) $
  15 // $Revision: 49267 $
  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