1 2 #ifndef BOOST_MPL_MAP_AUX_AT_IMPL_HPP_INCLUDED 3 #define BOOST_MPL_MAP_AUX_AT_IMPL_HPP_INCLUDED 4 5 // Copyright Aleksey Gurtovoy 2003-2004 6 // Copyright David Abrahams 2003-2004 7 // 8 // Distributed under the Boost Software License, Version 1.0. 9 // (See accompanying file LICENSE_1_0.txt or copy at 10 // http://www.boost.org/LICENSE_1_0.txt) 11 // 12 // See http://www.boost.org/libs/mpl for documentation. 13 14 // $Id$ 15 // $Date$ 16 // $Revision$ 17 18 #include <boost/mpl/at_fwd.hpp> 19 #include <boost/mpl/long.hpp> 20 #include <boost/mpl/map/aux_/tag.hpp> 21 #include <boost/mpl/aux_/order_impl.hpp> 22 #include <boost/mpl/aux_/overload_names.hpp> 23 #include <boost/mpl/aux_/type_wrapper.hpp> 24 #include <boost/mpl/aux_/ptr_to_ref.hpp> 25 #include <boost/mpl/aux_/static_cast.hpp> 26 #include <boost/mpl/aux_/config/typeof.hpp> 27 #include <boost/mpl/aux_/config/ctps.hpp> 28 29 #if !defined(BOOST_MPL_CFG_TYPEOF_BASED_SEQUENCES) 30 # include <boost/mpl/eval_if.hpp> 31 # include <boost/mpl/pair.hpp> 32 # include <boost/mpl/void.hpp> 33 # include <boost/mpl/aux_/config/static_constant.hpp> 34 #endif 35 36 namespace boost { namespace mpl { 37 38 #if defined(BOOST_MPL_CFG_TYPEOF_BASED_SEQUENCES) 39 40 template< typename Map, typename Key > 41 struct m_at 42 { 43 typedef aux::type_wrapper<Key> key_; 44 typedef __typeof__( BOOST_MPL_AUX_OVERLOAD_CALL_VALUE_BY_KEY( 45 Map 46 , BOOST_MPL_AUX_STATIC_CAST(key_*, 0) 47 ) ) type; 48 }; 49 50 template<> 51 struct at_impl< aux::map_tag > 52 { 53 template< typename Map, typename Key > struct apply 54 : aux::wrapped_type< typename m_at< 55 Map 56 , Key 57 >::type > 58 { 59 }; 60 }; 61 62 // agurt 31/jan/04: two-step implementation for the sake of GCC 3.x 63 template< typename Map, long order > 64 struct item_by_order_impl 65 { 66 typedef __typeof__( BOOST_MPL_AUX_OVERLOAD_CALL_ITEM_BY_ORDER( 67 Map 68 , BOOST_MPL_AUX_STATIC_CAST(long_<order>*, 0) 69 ) ) type; 70 }; 71 72 template< typename Map, long order > 73 struct item_by_order 74 : aux::wrapped_type< 75 typename item_by_order_impl<Map,order>::type 76 > 77 { 78 }; 79 80 #else // BOOST_MPL_CFG_TYPEOF_BASED_SEQUENCES 81 82 # if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) 83 84 template< typename Map, long n > struct m_at 85 { 86 typedef void_ type; 87 }; 88 89 # else 90 91 template< long n > struct m_at_impl 92 { 93 template< typename Map > struct result_ 94 { 95 typedef void_ type; 96 }; 97 }; 98 99 template< typename Map, long n > struct m_at 100 { 101 typedef typename m_at_impl<n>::result_<Map>::type type; 102 }; 103 104 # endif 105 106 107 template<> 108 struct at_impl< aux::map_tag > 109 { 110 template< typename Map, typename Key > struct apply 111 { 112 typedef typename m_at< Map, (x_order_impl<Map,Key>::value - 2) >::type item_; 113 typedef typename eval_if< 114 is_void_<item_> 115 , void_ 116 , second<item_> 117 >::type type; 118 }; 119 }; 120 121 template< typename Map, long order > struct is_item_masked 122 { 123 BOOST_STATIC_CONSTANT(bool, value = 124 sizeof( BOOST_MPL_AUX_OVERLOAD_CALL_IS_MASKED( 125 Map 126 , BOOST_MPL_AUX_STATIC_CAST(long_<order>*, 0) 127 ) ) == sizeof(aux::yes_tag) 128 ); 129 }; 130 131 template< typename Map, long order > struct item_by_order 132 { 133 typedef typename eval_if_c< 134 is_item_masked<Map,order>::value 135 , void_ 136 , m_at<Map,(order - 2)> 137 >::type type; 138 }; 139 140 #endif 141 142 }} 143 144 #endif // BOOST_MPL_SET_AUX_AT_IMPL_HPP_INCLUDED 145