1 /*============================================================================= 2 Copyright (c) 1998-2003 Joel de Guzman 3 Copyright (c) 2001 Daniel Nuffer 4 Copyright (c) 2002 Hartmut Kaiser 5 http://spirit.sourceforge.net/ 6 7 Distributed under the Boost Software License, Version 1.0. (See accompanying 8 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 9 =============================================================================*/ 10 #if !defined(BOOST_SPIRIT_ALTERNATIVE_HPP) 11 #define BOOST_SPIRIT_ALTERNATIVE_HPP 12 13 #include <boost/spirit/home/classic/namespace.hpp> 14 #include <boost/spirit/home/classic/core/parser.hpp> 15 #include <boost/spirit/home/classic/core/primitives/primitives.hpp> 16 #include <boost/spirit/home/classic/core/composite/composite.hpp> 17 #include <boost/spirit/home/classic/meta/as_parser.hpp> 18 19 namespace boost { namespace spirit { 20 21 BOOST_SPIRIT_CLASSIC_NAMESPACE_BEGIN 22 23 /////////////////////////////////////////////////////////////////////////// 24 // 25 // alternative class 26 // 27 // Handles expressions of the form: 28 // 29 // a | b 30 // 31 // where a and b are parsers. The expression returns a composite 32 // parser that matches a or b. One (not both) of the operands may 33 // be a literal char, wchar_t or a primitive string char const*, 34 // wchar_t const*. 35 // 36 // The expression is short circuit evaluated. b is never touched 37 // when a is returns a successful match. 38 // 39 /////////////////////////////////////////////////////////////////////////// 40 struct alternative_parser_gen; 41 42 #if BOOST_WORKAROUND(BOOST_MSVC, >= 1400) 43 #pragma warning(push) 44 #pragma warning(disable:4512) //assignment operator could not be generated 45 #endif 46 47 template <typename A, typename B> 48 struct alternative 49 : public binary<A, B, parser<alternative<A, B> > > 50 { 51 typedef alternative<A, B> self_t; 52 typedef binary_parser_category parser_category_t; 53 typedef alternative_parser_gen parser_generator_t; 54 typedef binary<A, B, parser<self_t> > base_t; 55 alternativeboost::spirit::alternative56 alternative(A const& a, B const& b) 57 : base_t(a, b) {} 58 59 template <typename ScannerT> 60 typename parser_result<self_t, ScannerT>::type parseboost::spirit::alternative61 parse(ScannerT const& scan) const 62 { 63 typedef typename parser_result<self_t, ScannerT>::type result_t; 64 typedef typename ScannerT::iterator_t iterator_t; 65 { // scope for save 66 iterator_t save = scan.first; 67 if (result_t hit = this->left().parse(scan)) 68 return hit; 69 scan.first = save; 70 } 71 return this->right().parse(scan); 72 } 73 }; 74 75 #if BOOST_WORKAROUND(BOOST_MSVC, >= 1400) 76 #pragma warning(pop) 77 #endif 78 79 struct alternative_parser_gen 80 { 81 template <typename A, typename B> 82 struct result 83 { 84 typedef 85 alternative< 86 typename as_parser<A>::type 87 , typename as_parser<B>::type 88 > 89 type; 90 }; 91 92 template <typename A, typename B> 93 static alternative< 94 typename as_parser<A>::type 95 , typename as_parser<B>::type 96 > generateboost::spirit::alternative_parser_gen97 generate(A const& a, B const& b) 98 { 99 return alternative<BOOST_DEDUCED_TYPENAME as_parser<A>::type, 100 BOOST_DEDUCED_TYPENAME as_parser<B>::type> 101 (as_parser<A>::convert(a), as_parser<B>::convert(b)); 102 } 103 }; 104 105 template <typename A, typename B> 106 alternative<A, B> 107 operator|(parser<A> const& a, parser<B> const& b); 108 109 template <typename A> 110 alternative<A, chlit<char> > 111 operator|(parser<A> const& a, char b); 112 113 template <typename B> 114 alternative<chlit<char>, B> 115 operator|(char a, parser<B> const& b); 116 117 template <typename A> 118 alternative<A, strlit<char const*> > 119 operator|(parser<A> const& a, char const* b); 120 121 template <typename B> 122 alternative<strlit<char const*>, B> 123 operator|(char const* a, parser<B> const& b); 124 125 template <typename A> 126 alternative<A, chlit<wchar_t> > 127 operator|(parser<A> const& a, wchar_t b); 128 129 template <typename B> 130 alternative<chlit<wchar_t>, B> 131 operator|(wchar_t a, parser<B> const& b); 132 133 template <typename A> 134 alternative<A, strlit<wchar_t const*> > 135 operator|(parser<A> const& a, wchar_t const* b); 136 137 template <typename B> 138 alternative<strlit<wchar_t const*>, B> 139 operator|(wchar_t const* a, parser<B> const& b); 140 141 BOOST_SPIRIT_CLASSIC_NAMESPACE_END 142 143 }} // namespace BOOST_SPIRIT_CLASSIC_NS 144 145 #endif 146 147 #include <boost/spirit/home/classic/core/composite/impl/alternative.ipp> 148