src/thirdparty/boost_1_47_0/boost/iterator/detail/minimum_category.hpp

   1 // Copyright David Abrahams 2003. Use, modification and distribution is
   2 // subject to the Boost 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 MINIMUM_CATEGORY_DWA20031119_HPP
   5 # define MINIMUM_CATEGORY_DWA20031119_HPP
   6
   7 # include <boost/type_traits/is_convertible.hpp>
   8 # include <boost/type_traits/is_same.hpp>
   9
  10 # include <boost/mpl/aux_/lambda_support.hpp>
  11
  12 namespace boost { namespace detail {
  13 //
  14 // Returns the minimum category type or error_type
  15 // if T1 and T2 are unrelated.
  16 //
  17 // For compilers not supporting is_convertible this only
  18 // works with the new boost return and traversal category
  19 // types. The exact boost _types_ are required. No derived types
  20 // will work.
  21 //
  22 //
  23 template <bool GreaterEqual, bool LessEqual>
  24 struct minimum_category_impl
  25 # if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
  26 {
  27     template <class T1, class T2> struct apply
  28     {
  29         typedef T2 type;
  30     };
  31     typedef void type;
  32 }
  33 # endif
  34 ;
  35
  36 template <class T1, class T2>
  37 struct error_not_related_by_convertibility;
  38
  39 template <>
  40 struct minimum_category_impl<true,false>
  41 {
  42     template <class T1, class T2> struct apply
  43     {
  44         typedef T2 type;
  45     };
  46 };
  47
  48 template <>
  49 struct minimum_category_impl<false,true>
  50 {
  51     template <class T1, class T2> struct apply
  52     {
  53         typedef T1 type;
  54     };
  55 };
  56
  57 template <>
  58 struct minimum_category_impl<true,true>
  59 {
  60     template <class T1, class T2> struct apply
  61     {
  62         BOOST_STATIC_ASSERT((is_same<T1,T2>::value));
  63         typedef T1 type;
  64     };
  65 };
  66
  67 template <>
  68 struct minimum_category_impl<false,false>
  69 {
  70     template <class T1, class T2> struct apply
  71     : error_not_related_by_convertibility<T1,T2>
  72     {
  73     };
  74 };
  75
  76 template <class T1 = mpl::_1, class T2 = mpl::_2>
  77 struct minimum_category
  78 {
  79     typedef minimum_category_impl<
  80 # if BOOST_WORKAROUND(BOOST_MSVC, < 1300) // ETI workaround
  81         is_same<T2,int>::value ||
  82 # endif
  83         ::boost::is_convertible<T1,T2>::value
  84       , ::boost::is_convertible<T2,T1>::value
  85 # if BOOST_WORKAROUND(BOOST_MSVC, < 1300) // ETI workaround
  86         || is_same<T1,int>::value
  87 # endif
  88     > outer;
  89
  90     typedef typename outer::template apply<T1,T2> inner;
  91     typedef typename inner::type type;
  92
  93     BOOST_MPL_AUX_LAMBDA_SUPPORT(2,minimum_category,(T1,T2))
  94 };
  95
  96 template <>
  97 struct minimum_category<mpl::_1,mpl::_2>
  98 {
  99     template <class T1, class T2>
 100     struct apply : minimum_category<T1,T2>
 101     {};
 102
 103     BOOST_MPL_AUX_LAMBDA_SUPPORT_SPEC(2,minimum_category,(mpl::_1,mpl::_2))
 104 };
 105
 106 # if BOOST_WORKAROUND(BOOST_MSVC, < 1300) // ETI workaround
 107 template <>
 108 struct minimum_category<int,int>
 109 {
 110     typedef int type;
 111 };
 112 # endif
 113
 114 }} // namespace boost::detail
 115
 116 #endif // MINIMUM_CATEGORY_DWA20031119_HPP