1 /*============================================================================= 2 Copyright (c) 2001-2011 Hartmut Kaiser 3 4 Distributed under the Boost Software License, Version 1.0. (See accompanying 5 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 6 =============================================================================*/ 7 #if !defined(SPIRIT_ALTERNATIVE_FUNCTION_APRIL_23_2007_1046AM) 8 #define SPIRIT_ALTERNATIVE_FUNCTION_APRIL_23_2007_1046AM 9 10 #if defined(_MSC_VER) 11 #pragma once 12 #endif 13 14 #include <boost/spirit/home/qi/domain.hpp> 15 #include <boost/spirit/home/qi/detail/assign_to.hpp> 16 #include <boost/spirit/home/support/unused.hpp> 17 #include <boost/spirit/home/qi/detail/attributes.hpp> 18 #include <boost/variant.hpp> 19 #include <boost/mpl/bool.hpp> 20 21 namespace boost { namespace spirit { namespace qi { namespace detail 22 { 23 template <typename Variant, typename Expected> 24 struct find_substitute 25 { 26 // Get the type from the variant that can be a substitute for Expected. 27 // If none is found, just return Expected 28 29 typedef Variant variant_type; 30 typedef typename variant_type::types types; 31 typedef typename mpl::end<types>::type end; 32 33 typedef typename mpl::find<types, Expected>::type iter_1; 34 35 typedef typename 36 mpl::eval_if< 37 is_same<iter_1, end>, 38 mpl::find_if<types, traits::is_substitute<mpl::_1, Expected> >, 39 mpl::identity<iter_1> 40 >::type 41 iter; 42 43 typedef typename 44 mpl::eval_if< 45 is_same<iter, end>, 46 mpl::identity<Expected>, 47 mpl::deref<iter> 48 >::type 49 type; 50 }; 51 52 template <typename Iterator, typename Context, typename Skipper, 53 typename Attribute> 54 struct alternative_function 55 { alternative_functionboost::spirit::qi::detail::alternative_function56 alternative_function( 57 Iterator& first_, Iterator const& last_, Context& context_, 58 Skipper const& skipper_, Attribute& attr_) 59 : first(first_), last(last_), context(context_), skipper(skipper_), 60 attr(attr_) 61 { 62 } 63 64 template <typename Component> callboost::spirit::qi::detail::alternative_function65 bool call(Component const& component, mpl::true_) const 66 { 67 // if Attribute is not a variant, then pass it as-is 68 return component.parse(first, last, context, skipper, attr); 69 } 70 71 template <typename Component> call_optional_or_variantboost::spirit::qi::detail::alternative_function72 bool call_optional_or_variant(Component const& component, mpl::true_) const 73 { 74 // If Attribute is an optional, then create an attribute for the Component 75 // with the type optional::value_type. If the expected attribute is unused type, 76 // use it instead. 77 typedef typename 78 traits::attribute_of<Component, Context, Iterator>::type 79 expected_type; 80 81 typename mpl::if_< 82 is_same<expected_type, unused_type>, 83 unused_type, 84 typename Attribute::value_type>::type 85 val; 86 87 if (component.parse(first, last, context, skipper, val)) 88 { 89 traits::assign_to(val, attr); 90 return true; 91 } 92 return false; 93 } 94 95 template <typename Component> call_variantboost::spirit::qi::detail::alternative_function96 bool call_variant(Component const& component, mpl::false_) const 97 { 98 // If Attribute is a variant, then search the variant types for a 99 // suitable substitute type. 100 101 typename 102 find_substitute<Attribute, 103 typename traits::attribute_of<Component, Context, Iterator>::type 104 >::type 105 val; 106 107 if (component.parse(first, last, context, skipper, val)) 108 { 109 traits::assign_to(val, attr); 110 return true; 111 } 112 return false; 113 } 114 115 template <typename Component> call_variantboost::spirit::qi::detail::alternative_function116 bool call_variant(Component const& component, mpl::true_) const 117 { 118 // If Attribute is a variant and the expected attribute is 119 // the same type (pass the variant as-is). 120 121 return component.parse(first, last, context, skipper, attr); 122 } 123 124 template <typename Component> call_optional_or_variantboost::spirit::qi::detail::alternative_function125 bool call_optional_or_variant(Component const& component, mpl::false_) const 126 { 127 // Attribute is a variant... 128 129 typedef typename 130 traits::attribute_of<Component, Context, Iterator>::type 131 expected; 132 return call_variant(component, 133 is_same<Attribute, expected>()); 134 } 135 136 template <typename Component> callboost::spirit::qi::detail::alternative_function137 bool call(Component const& component, mpl::false_) const 138 { 139 return call_optional_or_variant( 140 component, spirit::traits::not_is_variant<Attribute, qi::domain>()); 141 } 142 143 template <typename Component> call_unusedboost::spirit::qi::detail::alternative_function144 bool call_unused(Component const& component, mpl::true_) const 145 { 146 // return true if the parser succeeds 147 return call(component, 148 mpl::and_< 149 spirit::traits::not_is_variant<Attribute, qi::domain>, 150 spirit::traits::not_is_optional<Attribute, qi::domain> 151 >()); 152 } 153 154 template <typename Component> call_unusedboost::spirit::qi::detail::alternative_function155 bool call_unused(Component const& component, mpl::false_) const 156 { 157 return component.parse(first, last, context, skipper, unused); 158 } 159 160 template <typename Component> operator ()boost::spirit::qi::detail::alternative_function161 bool operator()(Component const& component) const 162 { 163 // return true if the parser succeeds 164 typedef typename traits::not_is_unused< 165 typename traits::attribute_of<Component, Context, Iterator>::type 166 >::type predicate; 167 168 return call_unused(component, predicate()); 169 } 170 171 Iterator& first; 172 Iterator const& last; 173 Context& context; 174 Skipper const& skipper; 175 Attribute& attr; 176 177 // silence MSVC warning C4512: assignment operator could not be generated 178 BOOST_DELETED_FUNCTION(alternative_function& operator= (alternative_function const&)) 179 }; 180 181 template <typename Iterator, typename Context, typename Skipper> 182 struct alternative_function<Iterator, Context, Skipper, unused_type const> 183 { alternative_functionboost::spirit::qi::detail::alternative_function184 alternative_function( 185 Iterator& first_, Iterator const& last_, Context& context_, 186 Skipper const& skipper_, unused_type) 187 : first(first_), last(last_), context(context_), skipper(skipper_) 188 { 189 } 190 191 template <typename Component> operator ()boost::spirit::qi::detail::alternative_function192 bool operator()(Component const& component) const 193 { 194 // return true if the parser succeeds 195 return component.parse(first, last, context, skipper, 196 unused); 197 } 198 199 Iterator& first; 200 Iterator const& last; 201 Context& context; 202 Skipper const& skipper; 203 204 // silence MSVC warning C4512: assignment operator could not be generated 205 BOOST_DELETED_FUNCTION(alternative_function& operator= (alternative_function const&)) 206 }; 207 208 }}}} 209 210 #endif 211