1 | |
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2 | #ifndef BOOST_MPL_IF_HPP_INCLUDED |
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3 | #define BOOST_MPL_IF_HPP_INCLUDED |
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4 | |
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5 | // Copyright Aleksey Gurtovoy 2000-2004 |
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6 | // |
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7 | // Distributed under the Boost Software License, Version 1.0. |
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8 | // (See accompanying file LICENSE_1_0.txt or copy at |
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9 | // http://www.boost.org/LICENSE_1_0.txt) |
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10 | // |
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11 | // See http://www.boost.org/libs/mpl for documentation. |
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12 | |
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13 | // $Id: if.hpp 49267 2008-10-11 06:19:02Z agurtovoy $ |
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14 | // $Date: 2008-10-11 02:19:02 -0400 (Sat, 11 Oct 2008) $ |
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15 | // $Revision: 49267 $ |
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16 | |
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17 | #include <boost/mpl/aux_/value_wknd.hpp> |
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18 | #include <boost/mpl/aux_/static_cast.hpp> |
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19 | #include <boost/mpl/aux_/na_spec.hpp> |
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20 | #include <boost/mpl/aux_/lambda_support.hpp> |
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21 | #include <boost/mpl/aux_/config/integral.hpp> |
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22 | #include <boost/mpl/aux_/config/ctps.hpp> |
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23 | #include <boost/mpl/aux_/config/workaround.hpp> |
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24 | |
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25 | namespace boost { namespace mpl { |
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26 | |
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27 | #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) |
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28 | |
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29 | template< |
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30 | bool C |
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31 | , typename T1 |
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32 | , typename T2 |
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33 | > |
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34 | struct if_c |
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35 | { |
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36 | typedef T1 type; |
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37 | }; |
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38 | |
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39 | template< |
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40 | typename T1 |
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41 | , typename T2 |
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42 | > |
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43 | struct if_c<false,T1,T2> |
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44 | { |
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45 | typedef T2 type; |
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46 | }; |
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47 | |
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48 | // agurt, 05/sep/04: nondescriptive parameter names for the sake of DigitalMars |
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49 | // (and possibly MWCW < 8.0); see http://article.gmane.org/gmane.comp.lib.boost.devel/108959 |
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50 | template< |
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51 | typename BOOST_MPL_AUX_NA_PARAM(T1) |
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52 | , typename BOOST_MPL_AUX_NA_PARAM(T2) |
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53 | , typename BOOST_MPL_AUX_NA_PARAM(T3) |
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54 | > |
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55 | struct if_ |
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56 | { |
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57 | private: |
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58 | // agurt, 02/jan/03: two-step 'type' definition for the sake of aCC |
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59 | typedef if_c< |
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60 | #if defined(BOOST_MPL_CFG_BCC_INTEGRAL_CONSTANTS) |
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61 | BOOST_MPL_AUX_VALUE_WKND(T1)::value |
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62 | #else |
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63 | BOOST_MPL_AUX_STATIC_CAST(bool, BOOST_MPL_AUX_VALUE_WKND(T1)::value) |
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64 | #endif |
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65 | , T2 |
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66 | , T3 |
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67 | > almost_type_; |
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68 | |
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69 | public: |
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70 | typedef typename almost_type_::type type; |
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71 | |
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72 | BOOST_MPL_AUX_LAMBDA_SUPPORT(3,if_,(T1,T2,T3)) |
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73 | }; |
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74 | |
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75 | #else |
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76 | |
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77 | // no partial class template specialization |
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78 | |
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79 | namespace aux { |
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80 | |
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81 | template< bool C > |
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82 | struct if_impl |
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83 | { |
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84 | template< typename T1, typename T2 > struct result_ |
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85 | { |
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86 | typedef T1 type; |
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87 | }; |
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88 | }; |
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89 | |
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90 | template<> |
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91 | struct if_impl<false> |
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92 | { |
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93 | template< typename T1, typename T2 > struct result_ |
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94 | { |
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95 | typedef T2 type; |
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96 | }; |
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97 | }; |
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98 | |
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99 | } // namespace aux |
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100 | |
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101 | template< |
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102 | bool C_ |
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103 | , typename T1 |
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104 | , typename T2 |
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105 | > |
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106 | struct if_c |
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107 | { |
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108 | typedef typename aux::if_impl< C_ > |
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109 | ::template result_<T1,T2>::type type; |
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110 | }; |
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111 | |
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112 | // (almost) copy & paste in order to save one more |
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113 | // recursively nested template instantiation to user |
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114 | template< |
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115 | typename BOOST_MPL_AUX_NA_PARAM(C_) |
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116 | , typename BOOST_MPL_AUX_NA_PARAM(T1) |
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117 | , typename BOOST_MPL_AUX_NA_PARAM(T2) |
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118 | > |
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119 | struct if_ |
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120 | { |
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121 | enum { msvc_wknd_ = BOOST_MPL_AUX_MSVC_VALUE_WKND(C_)::value }; |
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122 | |
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123 | typedef typename aux::if_impl< BOOST_MPL_AUX_STATIC_CAST(bool, msvc_wknd_) > |
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124 | ::template result_<T1,T2>::type type; |
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125 | |
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126 | BOOST_MPL_AUX_LAMBDA_SUPPORT(3,if_,(C_,T1,T2)) |
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127 | }; |
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128 | |
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129 | #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION |
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130 | |
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131 | BOOST_MPL_AUX_NA_SPEC(3, if_) |
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132 | |
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133 | }} |
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134 | |
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135 | #endif // BOOST_MPL_IF_HPP_INCLUDED |
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