1 // Copyright David Abrahams 2002. 2 // Distributed under the Boost Software License, Version 1.0. (See 3 // accompanying file LICENSE_1_0.txt or copy at 4 // http://www.boost.org/LICENSE_1_0.txt) 5 #ifndef IF_ELSE_DWA2002322_HPP 6 # define IF_ELSE_DWA2002322_HPP 7 # include <boost/config.hpp> 8 9 namespace boost { namespace python { namespace detail { 10 11 template <class T> struct elif_selected; 12 13 template <class T> 14 struct if_selected 15 { 16 template <bool b> 17 struct elif : elif_selected<T> 18 { 19 }; 20 21 template <class U> 22 struct else_ 23 { 24 typedef T type; 25 }; 26 }; 27 28 # if defined(BOOST_MSVC) && (BOOST_MSVC == 1300) 29 namespace msvc70_aux { 30 31 template< bool > struct inherit_from 32 { 33 template< typename T > struct result 34 { 35 typedef T type; 36 }; 37 }; 38 39 template<> struct inherit_from<true> 40 { 41 template< typename T > struct result 42 { 43 struct type {}; 44 }; 45 }; 46 47 template< typename T > 48 struct never_true 49 { 50 BOOST_STATIC_CONSTANT(bool, value = false); 51 }; 52 53 } // namespace msvc70_aux 54 55 #endif // # if defined(BOOST_MSVC) && (BOOST_MSVC == 1300) 56 57 template <class T> 58 struct elif_selected 59 { 60 # if !(defined(BOOST_MSVC) && BOOST_MSVC <= 1300 || defined(__MWERKS__) && __MWERKS__ <= 0x2407) 61 template <class U> class then; 62 # elif defined(BOOST_MSVC) && (BOOST_MSVC == 1300) 63 template <class U> 64 struct then : msvc70_aux::inherit_from< msvc70_aux::never_true<U>::value > 65 ::template result< if_selected<T> >::type 66 { 67 }; 68 # else 69 template <class U> 70 struct then : if_selected<T> 71 { 72 }; 73 # endif 74 }; 75 76 # if !(defined(BOOST_MSVC) && BOOST_MSVC <= 1300 || defined(__MWERKS__) && __MWERKS__ <= 0x2407) 77 template <class T> 78 template <class U> 79 class elif_selected<T>::then : public if_selected<T> 80 { 81 }; 82 # endif 83 84 template <bool b> struct if_ 85 { 86 template <class T> 87 struct then : if_selected<T> 88 { 89 }; 90 }; 91 92 struct if_unselected 93 { 94 template <bool b> struct elif : if_<b> 95 { 96 }; 97 98 template <class U> 99 struct else_ 100 { 101 typedef U type; 102 }; 103 }; 104 105 template <> 106 struct if_<false> 107 { 108 template <class T> 109 struct then : if_unselected 110 { 111 }; 112 }; 113 114 }}} // namespace boost::python::detail 115 116 #endif // IF_ELSE_DWA2002322_HPP 117