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1 // Copyright David Abrahams 2003. Use, modification and distribution is |
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2 // subject to the Boost Software License, Version 1.0. (See accompanying |
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3 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
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4 #ifndef IS_READABLE_ITERATOR_DWA2003112_HPP |
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5 # define IS_READABLE_ITERATOR_DWA2003112_HPP |
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6 |
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7 #include <boost/mpl/bool.hpp> |
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8 #include <boost/detail/iterator.hpp> |
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9 |
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10 #include <boost/type_traits/detail/bool_trait_def.hpp> |
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11 #include <boost/iterator/detail/any_conversion_eater.hpp> |
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12 |
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13 // should be the last #include |
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14 #include <boost/iterator/detail/config_def.hpp> |
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15 |
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16 #ifndef BOOST_NO_IS_CONVERTIBLE |
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17 |
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18 namespace boost { |
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19 |
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20 namespace detail |
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21 { |
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22 // Guts of is_readable_iterator. Value is the iterator's value_type |
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23 // and the result is computed in the nested rebind template. |
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24 template <class Value> |
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25 struct is_readable_iterator_impl |
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26 { |
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27 static char tester(Value&, int); |
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28 static char (& tester(any_conversion_eater, ...) )[2]; |
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29 |
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30 template <class It> |
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31 struct rebind |
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32 { |
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33 static It& x; |
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34 |
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35 BOOST_STATIC_CONSTANT( |
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36 bool |
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37 , value = ( |
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38 sizeof( |
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39 is_readable_iterator_impl<Value>::tester(*x, 1) |
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40 ) == 1 |
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41 ) |
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42 ); |
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43 }; |
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44 }; |
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45 |
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46 #undef BOOST_READABLE_PRESERVER |
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47 |
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48 // |
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49 // void specializations to handle std input and output iterators |
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50 // |
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51 template <> |
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52 struct is_readable_iterator_impl<void> |
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53 { |
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54 template <class It> |
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55 struct rebind : boost::mpl::false_ |
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56 {}; |
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57 }; |
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58 |
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59 #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS |
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60 template <> |
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61 struct is_readable_iterator_impl<const void> |
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62 { |
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63 template <class It> |
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64 struct rebind : boost::mpl::false_ |
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65 {}; |
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66 }; |
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67 |
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68 template <> |
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69 struct is_readable_iterator_impl<volatile void> |
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70 { |
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71 template <class It> |
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72 struct rebind : boost::mpl::false_ |
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73 {}; |
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74 }; |
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75 |
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76 template <> |
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77 struct is_readable_iterator_impl<const volatile void> |
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78 { |
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79 template <class It> |
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80 struct rebind : boost::mpl::false_ |
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81 {}; |
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82 }; |
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83 #endif |
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84 |
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85 // |
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86 // This level of dispatching is required for Borland. We might save |
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87 // an instantiation by removing it for others. |
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88 // |
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89 template <class It> |
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90 struct is_readable_iterator_impl2 |
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91 : is_readable_iterator_impl< |
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92 BOOST_DEDUCED_TYPENAME boost::detail::iterator_traits<It>::value_type const |
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93 >::template rebind<It> |
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94 {}; |
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95 } // namespace detail |
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96 |
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97 // Define the trait with full mpl lambda capability and various broken |
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98 // compiler workarounds |
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99 BOOST_TT_AUX_BOOL_TRAIT_DEF1( |
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100 is_readable_iterator,T,::boost::detail::is_readable_iterator_impl2<T>::value) |
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101 |
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102 } // namespace boost |
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103 |
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104 #endif |
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105 |
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106 #include <boost/iterator/detail/config_undef.hpp> |
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107 |
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108 #endif // IS_READABLE_ITERATOR_DWA2003112_HPP |