boost/iterator/is_readable_iterator.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 IS_READABLE_ITERATOR_DWA2003112_HPP
   5 # define IS_READABLE_ITERATOR_DWA2003112_HPP
   6
   7 #include <boost/mpl/bool.hpp>
   8 #include <boost/detail/iterator.hpp>
   9
  10 #include <boost/type_traits/detail/bool_trait_def.hpp>
  11 #include <boost/iterator/detail/any_conversion_eater.hpp>
  12
  13 // should be the last #include
  14 #include <boost/iterator/detail/config_def.hpp>
  15
  16 #ifndef BOOST_NO_IS_CONVERTIBLE
  17
  18 namespace boost {
  19
  20 namespace detail
  21 {
  22   // Guts of is_readable_iterator.  Value is the iterator's value_type
  23   // and the result is computed in the nested rebind template.
  24   template <class Value>
  25   struct is_readable_iterator_impl
  26   {
  27       static char tester(Value&, int);
  28       static char (& tester(any_conversion_eater, ...) )[2];
  29
  30       template <class It>
  31       struct rebind
  32       {
  33           static It& x;
  34
  35           BOOST_STATIC_CONSTANT(
  36               bool
  37             , value = (
  38                 sizeof(
  39                     is_readable_iterator_impl<Value>::tester(*x, 1)
  40                 ) == 1
  41             )
  42           );
  43       };
  44   };
  45
  46 #undef BOOST_READABLE_PRESERVER
  47
  48   //
  49   // void specializations to handle std input and output iterators
  50   //
  51   template <>
  52   struct is_readable_iterator_impl<void>
  53   {
  54       template <class It>
  55       struct rebind : boost::mpl::false_
  56       {};
  57   };
  58
  59 #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
  60   template <>
  61   struct is_readable_iterator_impl<const void>
  62   {
  63       template <class It>
  64       struct rebind : boost::mpl::false_
  65       {};
  66   };
  67
  68   template <>
  69   struct is_readable_iterator_impl<volatile void>
  70   {
  71       template <class It>
  72       struct rebind : boost::mpl::false_
  73       {};
  74   };
  75
  76   template <>
  77   struct is_readable_iterator_impl<const volatile void>
  78   {
  79       template <class It>
  80       struct rebind : boost::mpl::false_
  81       {};
  82   };
  83 #endif
  84
  85   //
  86   // This level of dispatching is required for Borland.  We might save
  87   // an instantiation by removing it for others.
  88   //
  89   template <class It>
  90   struct is_readable_iterator_impl2
  91     : is_readable_iterator_impl<
  92           BOOST_DEDUCED_TYPENAME boost::detail::iterator_traits<It>::value_type const
  93       >::template rebind<It>
  94   {};
  95 } // namespace detail
  96
  97 // Define the trait with full mpl lambda capability and various broken
  98 // compiler workarounds
  99 BOOST_TT_AUX_BOOL_TRAIT_DEF1(
 100     is_readable_iterator,T,::boost::detail::is_readable_iterator_impl2<T>::value)
 101
 102 } // namespace boost
 103
 104 #endif
 105
 106 #include <boost/iterator/detail/config_undef.hpp>
 107
 108 #endif // IS_READABLE_ITERATOR_DWA2003112_HPP