boost/xpressive/detail/core/matcher/predicate_matcher.hpp

   1 ///////////////////////////////////////////////////////////////////////////////
   2 // predicate_matcher.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_CORE_MATCHER_PREDICATE_MATCHER_HPP_EAN_03_22_2007
   9 #define BOOST_XPRESSIVE_DETAIL_CORE_MATCHER_PREDICATE_MATCHER_HPP_EAN_03_22_2007
  10
  11 // MS compatible compilers support #pragma once
  12 #if defined(_MSC_VER)
  13 # pragma once
  14 #endif
  15
  16 #include <boost/mpl/not.hpp>
  17 #include <boost/mpl/placeholders.hpp>
  18 #include <boost/xpressive/detail/detail_fwd.hpp>
  19 #include <boost/xpressive/detail/core/quant_style.hpp>
  20 #include <boost/xpressive/detail/core/matcher/action_matcher.hpp>
  21 #include <boost/xpressive/detail/core/state.hpp>
  22 #include <boost/proto/core.hpp>
  23
  24 namespace boost { namespace xpressive { namespace detail
  25 {
  26     ///////////////////////////////////////////////////////////////////////////////
  27     // predicate_context
  28     //
  29     template<typename BidiIter>
  30     struct predicate_context
  31     {
  32         explicit predicate_context(int sub, sub_match_impl<BidiIter> const *sub_matches, action_args_type *action_args)
  33           : sub_(sub)
  34           , sub_matches_(sub_matches)
  35           , action_args_(action_args)
  36         {}
  37
  38         action_args_type const &args() const
  39         {
  40             return *this->action_args_;
  41         }
  42
  43         // eval_terminal
  44         template<typename Expr, typename Arg>
  45         struct eval_terminal
  46           : proto::default_eval<Expr, predicate_context const>
  47         {};
  48
  49         template<typename Expr, typename Arg>
  50         struct eval_terminal<Expr, reference_wrapper<Arg> >
  51         {
  52             typedef Arg &result_type;
  53             result_type operator()(Expr &expr, predicate_context const &) const
  54             {
  55                 return proto::value(expr).get();
  56             }
  57         };
  58
  59         template<typename Expr>
  60         struct eval_terminal<Expr, any_matcher>
  61         {
  62             typedef sub_match<BidiIter> const &result_type;
  63             result_type operator()(Expr &, predicate_context const &ctx) const
  64             {
  65                 return ctx.sub_matches_[ctx.sub_];
  66             }
  67         };
  68
  69         template<typename Expr>
  70         struct eval_terminal<Expr, mark_placeholder>
  71         {
  72             typedef sub_match<BidiIter> const &result_type;
  73             result_type operator()(Expr &expr, predicate_context const &ctx) const
  74             {
  75                 return ctx.sub_matches_[proto::value(expr).mark_number_];
  76             }
  77         };
  78
  79         template<typename Expr, typename Type, typename Int>
  80         struct eval_terminal<Expr, action_arg<Type, Int> >
  81         {
  82             typedef typename action_arg<Type, Int>::reference result_type;
  83             result_type operator()(Expr &expr, predicate_context const &ctx) const
  84             {
  85                 action_args_type::const_iterator where_ = ctx.args().find(&typeid(proto::value(expr)));
  86                 if(where_ == ctx.args().end())
  87                 {
  88                     BOOST_THROW_EXCEPTION(
  89                         regex_error(
  90                             regex_constants::error_badarg
  91                           , "An argument to an action was unspecified"
  92                         )
  93                     );
  94                 }
  95                 return proto::value(expr).cast(where_->second);
  96             }
  97         };
  98
  99         // eval
 100         template<typename Expr, typename Tag = typename Expr::proto_tag>
 101         struct eval
 102           : proto::default_eval<Expr, predicate_context const>
 103         {};
 104
 105         template<typename Expr>
 106         struct eval<Expr, proto::tag::terminal>
 107           : eval_terminal<Expr, typename proto::result_of::value<Expr>::type>
 108         {};
 109
 110         #if BOOST_VERSION >= 103500
 111         template<typename Expr>
 112         struct eval<Expr, proto::tag::mem_ptr>
 113           : mem_ptr_eval<Expr, predicate_context const>
 114         {};
 115         #endif
 116
 117         int sub_;
 118         sub_match_impl<BidiIter> const *sub_matches_;
 119         action_args_type *action_args_;
 120     };
 121
 122     ///////////////////////////////////////////////////////////////////////////////
 123     // AssertionFunctor
 124     //
 125     struct AssertionFunctor
 126       : proto::function<
 127             proto::terminal<check_tag>
 128           , proto::terminal<proto::_>
 129         >
 130     {};
 131
 132     ///////////////////////////////////////////////////////////////////////////////
 133     // predicate_matcher
 134     //
 135     template<typename Predicate>
 136     struct predicate_matcher
 137       : quant_style_assertion
 138     {
 139         int sub_;
 140         Predicate predicate_;
 141
 142         predicate_matcher(Predicate const &pred, int sub)
 143           : sub_(sub)
 144           , predicate_(pred)
 145         {
 146         }
 147
 148         template<typename BidiIter, typename Next>
 149         bool match(match_state<BidiIter> &state, Next const &next) const
 150         {
 151             // Predicate is check(assertion), where assertion can be
 152             // a lambda or a function object.
 153             return this->match_(state, next, proto::matches<Predicate, AssertionFunctor>());
 154         }
 155
 156     private:
 157         template<typename BidiIter, typename Next>
 158         bool match_(match_state<BidiIter> &state, Next const &next, mpl::true_) const
 159         {
 160             sub_match<BidiIter> const &sub = state.sub_match(this->sub_);
 161             return proto::value(proto::child_c<1>(this->predicate_))(sub) && next.match(state);
 162         }
 163
 164         template<typename BidiIter, typename Next>
 165         bool match_(match_state<BidiIter> &state, Next const &next, mpl::false_) const
 166         {
 167             predicate_context<BidiIter> ctx(this->sub_, state.sub_matches_, state.action_args_);
 168             return proto::eval(proto::child_c<1>(this->predicate_), ctx) && next.match(state);
 169         }
 170     };
 171
 172 }}}
 173
 174 #endif // BOOST_XPRESSIVE_DETAIL_CORE_MATCHER_PREDICATE_MATCHER_HPP_EAN_03_22_2007