1 /////////////////////////////////////////////////////////////////////////////// 2 // as_alternate.hpp 3 // 4 // Copyright 2008 Eric Niebler. Distributed under the Boost 5 // Software License, Version 1.0. (See accompanying file 6 // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 7 8 #ifndef BOOST_XPRESSIVE_DETAIL_STATIC_TRANSFORMS_AS_ALTERNATE_HPP_EAN_04_01_2007 9 #define BOOST_XPRESSIVE_DETAIL_STATIC_TRANSFORMS_AS_ALTERNATE_HPP_EAN_04_01_2007 10 11 // MS compatible compilers support #pragma once 12 #if defined(_MSC_VER) 13 # pragma once 14 #endif 15 16 #include <boost/config.hpp> 17 #include <boost/mpl/assert.hpp> 18 #include <boost/type_traits/is_same.hpp> 19 #include <boost/proto/core.hpp> 20 #include <boost/xpressive/detail/detail_fwd.hpp> 21 #include <boost/xpressive/detail/static/static.hpp> 22 #include <boost/xpressive/detail/core/matcher/alternate_matcher.hpp> 23 #include <boost/xpressive/detail/utility/cons.hpp> 24 25 namespace boost { namespace xpressive 26 { 27 namespace detail 28 { 29 /////////////////////////////////////////////////////////////////////////////// 30 // alternates_list 31 // a fusion-compatible sequence of alternate expressions, that also keeps 32 // track of the list's width and purity. 33 template<typename Head, typename Tail> 34 struct alternates_list 35 : fusion::cons<Head, Tail> 36 { 37 BOOST_STATIC_CONSTANT(std::size_t, width = Head::width == Tail::width ? Head::width : detail::unknown_width::value); 38 BOOST_STATIC_CONSTANT(bool, pure = Head::pure && Tail::pure); 39 alternates_listboost::xpressive::detail::alternates_list40 alternates_list(Head const &head, Tail const &tail) 41 : fusion::cons<Head, Tail>(head, tail) 42 { 43 } 44 }; 45 46 template<typename Head> 47 struct alternates_list<Head, fusion::nil> 48 : fusion::cons<Head, fusion::nil> 49 { 50 BOOST_STATIC_CONSTANT(std::size_t, width = Head::width); 51 BOOST_STATIC_CONSTANT(bool, pure = Head::pure); 52 alternates_listboost::xpressive::detail::alternates_list53 alternates_list(Head const &head, fusion::nil const &tail) 54 : fusion::cons<Head, fusion::nil>(head, tail) 55 { 56 } 57 }; 58 } 59 60 namespace grammar_detail 61 { 62 /////////////////////////////////////////////////////////////////////////////// 63 // in_alternate_list 64 template<typename Grammar, typename Callable = proto::callable> 65 struct in_alternate_list : proto::transform<in_alternate_list<Grammar, Callable> > 66 { 67 template<typename Expr, typename State, typename Data> 68 struct impl : proto::transform_impl<Expr, State, Data> 69 { 70 typedef 71 detail::alternates_list< 72 typename Grammar::template impl< 73 Expr 74 , detail::alternate_end_xpression 75 , Data 76 >::result_type 77 , State 78 > 79 result_type; 80 operator ()boost::xpressive::grammar_detail::in_alternate_list::impl81 result_type operator ()( 82 typename impl::expr_param expr 83 , typename impl::state_param state 84 , typename impl::data_param data 85 ) const 86 { 87 return result_type( 88 typename Grammar::template impl<Expr, detail::alternate_end_xpression, Data>()( 89 expr 90 , detail::alternate_end_xpression() 91 , data 92 ) 93 , state 94 ); 95 } 96 }; 97 }; 98 99 /////////////////////////////////////////////////////////////////////////////// 100 // as_alternate_matcher 101 template<typename Grammar, typename Callable = proto::callable> 102 struct as_alternate_matcher : proto::transform<as_alternate_matcher<Grammar, Callable> > 103 { 104 template<typename Expr, typename State, typename Data> 105 struct impl : proto::transform_impl<Expr, State, Data> 106 { 107 typedef typename impl::data data_type; 108 typedef 109 detail::alternate_matcher< 110 typename Grammar::template impl<Expr, State, Data>::result_type 111 , typename data_type::traits_type 112 > 113 result_type; 114 operator ()boost::xpressive::grammar_detail::as_alternate_matcher::impl115 result_type operator ()( 116 typename impl::expr_param expr 117 , typename impl::state_param state 118 , typename impl::data_param data 119 ) const 120 { 121 return result_type( 122 typename Grammar::template impl<Expr, State, Data>()(expr, state, data) 123 ); 124 } 125 }; 126 }; 127 } 128 129 }} 130 131 #endif 132