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1 // Copyright David Abrahams 2005. Distributed under the Boost |
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2 // 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 BOOST_PARAMETER_BINDING_DWA200558_HPP |
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5 # define BOOST_PARAMETER_BINDING_DWA200558_HPP |
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6 |
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7 # include <boost/mpl/apply.hpp> |
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8 # include <boost/mpl/assert.hpp> |
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9 # include <boost/mpl/and.hpp> |
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10 # include <boost/parameter/aux_/result_of0.hpp> |
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11 # include <boost/parameter/aux_/void.hpp> |
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12 # include <boost/type_traits/is_same.hpp> |
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13 |
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14 # if BOOST_WORKAROUND(BOOST_MSVC, < 1300) |
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15 # include <boost/mpl/eval_if.hpp> |
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16 # endif |
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17 |
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18 namespace boost { namespace parameter { |
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19 |
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20 // A metafunction that, given an argument pack, returns the type of |
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21 // the parameter identified by the given keyword. If no such |
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22 // parameter has been specified, returns Default |
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23 |
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24 # if BOOST_WORKAROUND(BOOST_MSVC, <= 1300) \ |
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25 || BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564)) |
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26 template <class Parameters, class Keyword, class Default> |
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27 struct binding0 |
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28 { |
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29 typedef typename mpl::apply_wrap3< |
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30 typename Parameters::binding,Keyword,Default,mpl::true_ |
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31 >::type type; |
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32 |
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33 BOOST_MPL_ASSERT_NOT(( |
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34 mpl::and_< |
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35 is_same<Default, void_> |
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36 , is_same<type, void_> |
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37 > |
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38 )); |
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39 }; |
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40 # endif |
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41 |
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42 template <class Parameters, class Keyword, class Default = void_> |
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43 # if !BOOST_WORKAROUND(BOOST_MSVC, < 1300) |
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44 struct binding |
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45 # else |
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46 struct binding_eti |
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47 # endif |
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48 { |
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49 # if BOOST_WORKAROUND(BOOST_MSVC, <= 1300) \ |
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50 || BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564)) |
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51 typedef typename mpl::eval_if< |
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52 mpl::is_placeholder<Parameters> |
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53 , mpl::identity<int> |
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54 , binding0<Parameters,Keyword,Default> |
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55 >::type type; |
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56 # else |
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57 typedef typename mpl::apply_wrap3< |
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58 typename Parameters::binding,Keyword,Default,mpl::true_ |
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59 >::type type; |
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60 |
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61 BOOST_MPL_ASSERT_NOT(( |
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62 mpl::and_< |
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63 is_same<Default, void_> |
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64 , is_same<type, void_> |
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65 > |
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66 )); |
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67 # endif |
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68 |
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69 # if !BOOST_WORKAROUND(BOOST_MSVC, < 1300) |
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70 BOOST_MPL_AUX_LAMBDA_SUPPORT(3,binding,(Parameters,Keyword,Default)) |
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71 # endif |
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72 }; |
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73 |
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74 # if BOOST_WORKAROUND(BOOST_MSVC, < 1300) |
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75 template <class Parameters, class Keyword, class Default = void_> |
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76 struct binding |
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77 { |
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78 typedef typename mpl::eval_if< |
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79 is_same<Parameters, int> |
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80 , mpl::identity<int> |
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81 , binding_eti<Parameters, Keyword, Default> |
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82 >::type type; |
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83 |
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84 BOOST_MPL_AUX_LAMBDA_SUPPORT(3,binding,(Parameters,Keyword,Default)) |
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85 }; |
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86 # endif |
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87 |
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88 // A metafunction that, given an argument pack, returns the type of |
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89 // the parameter identified by the given keyword. If no such |
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90 // parameter has been specified, returns the type returned by invoking |
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91 // DefaultFn |
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92 template <class Parameters, class Keyword, class DefaultFn> |
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93 struct lazy_binding |
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94 { |
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95 typedef typename mpl::apply_wrap3< |
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96 typename Parameters::binding |
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97 , Keyword |
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98 , typename aux::result_of0<DefaultFn>::type |
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99 , mpl::true_ |
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100 >::type type; |
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101 }; |
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102 |
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103 |
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104 }} // namespace boost::parameter |
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105 |
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106 #endif // BOOST_PARAMETER_BINDING_DWA200558_HPP |