1 | |
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2 | #ifndef BOOST_MPL_IF_HPP_INCLUDED |

3 | #define BOOST_MPL_IF_HPP_INCLUDED |

4 | |

5 | // Copyright Aleksey Gurtovoy 2000-2004 |

6 | // |

7 | // Distributed under the Boost Software License, Version 1.0. |

8 | // (See accompanying file LICENSE_1_0.txt or copy at |

9 | // http://www.boost.org/LICENSE_1_0.txt) |

10 | // |

11 | // See http://www.boost.org/libs/mpl for documentation. |

12 | |

13 | // $Id$ |

14 | // $Date$ |

15 | // $Revision$ |

16 | |

17 | #include <boost/mpl/aux_/value_wknd.hpp> |

18 | #include <boost/mpl/aux_/static_cast.hpp> |

19 | #include <boost/mpl/aux_/na_spec.hpp> |

20 | #include <boost/mpl/aux_/lambda_support.hpp> |

21 | #include <boost/mpl/aux_/config/integral.hpp> |

22 | #include <boost/mpl/aux_/config/ctps.hpp> |

23 | #include <boost/mpl/aux_/config/workaround.hpp> |

24 | |

25 | namespace boost { namespace mpl { |

26 | |

27 | #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) |

28 | |

29 | template< |

30 | bool C |

31 | , typename T1 |

32 | , typename T2 |

33 | > |

34 | struct if_c |

35 | { |

36 | typedef T1 type; |

37 | }; |

38 | |

39 | template< |

40 | typename T1 |

41 | , typename T2 |

42 | > |

43 | struct if_c<false,T1,T2> |

44 | { |

45 | typedef T2 type; |

46 | }; |

47 | |

48 | // agurt, 05/sep/04: nondescriptive parameter names for the sake of DigitalMars |

49 | // (and possibly MWCW < 8.0); see http://article.gmane.org/gmane.comp.lib.boost.devel/108959 |

50 | template< |

51 | typename BOOST_MPL_AUX_NA_PARAM(T1) |

52 | , typename BOOST_MPL_AUX_NA_PARAM(T2) |

53 | , typename BOOST_MPL_AUX_NA_PARAM(T3) |

54 | > |

55 | struct if_ |

56 | { |

57 | private: |

58 | // agurt, 02/jan/03: two-step 'type' definition for the sake of aCC |

59 | typedef if_c< |

60 | #if defined(BOOST_MPL_CFG_BCC_INTEGRAL_CONSTANTS) |

61 | BOOST_MPL_AUX_VALUE_WKND(T1)::value |

62 | #else |

63 | BOOST_MPL_AUX_STATIC_CAST(bool, BOOST_MPL_AUX_VALUE_WKND(T1)::value) |

64 | #endif |

65 | , T2 |

66 | , T3 |

67 | > almost_type_; |

68 | |

69 | public: |

70 | typedef typename almost_type_::type type; |

71 | |

72 | BOOST_MPL_AUX_LAMBDA_SUPPORT(3,if_,(T1,T2,T3)) |

73 | }; |

74 | |

75 | #else |

76 | |

77 | // no partial class template specialization |

78 | |

79 | namespace aux { |

80 | |

81 | template< bool C > |

82 | struct if_impl |

83 | { |

84 | template< typename T1, typename T2 > struct result_ |

85 | { |

86 | typedef T1 type; |

87 | }; |

88 | }; |

89 | |

90 | template<> |

91 | struct if_impl<false> |

92 | { |

93 | template< typename T1, typename T2 > struct result_ |

94 | { |

95 | typedef T2 type; |

96 | }; |

97 | }; |

98 | |

99 | } // namespace aux |

100 | |

101 | template< |

102 | bool C_ |

103 | , typename T1 |

104 | , typename T2 |

105 | > |

106 | struct if_c |

107 | { |

108 | typedef typename aux::if_impl< C_ > |

109 | ::template result_<T1,T2>::type type; |

110 | }; |

111 | |

112 | // (almost) copy & paste in order to save one more |

113 | // recursively nested template instantiation to user |

114 | template< |

115 | typename BOOST_MPL_AUX_NA_PARAM(C_) |

116 | , typename BOOST_MPL_AUX_NA_PARAM(T1) |

117 | , typename BOOST_MPL_AUX_NA_PARAM(T2) |

118 | > |

119 | struct if_ |

120 | { |

121 | enum { msvc_wknd_ = BOOST_MPL_AUX_MSVC_VALUE_WKND(C_)::value }; |

122 | |

123 | typedef typename aux::if_impl< BOOST_MPL_AUX_STATIC_CAST(bool, msvc_wknd_) > |

124 | ::template result_<T1,T2>::type type; |

125 | |

126 | BOOST_MPL_AUX_LAMBDA_SUPPORT(3,if_,(C_,T1,T2)) |

127 | }; |

128 | |

129 | #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION |

130 | |

131 | BOOST_MPL_AUX_NA_SPEC(3, if_) |

132 | |

133 | }} |

134 | |

135 | #endif // BOOST_MPL_IF_HPP_INCLUDED |

136 |