action_matcher.hpp

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///////////////////////////////////////////////////////////////////////////////
// action_matcher.hpp
//
//  Copyright 2008 Eric Niebler.
//  Copyright 2008 David Jenkins.
//
//  Distributed under the Boost Software License, Version 1.0. (See
//  accompanying file LICENSE_1_0.txt or copy at
//  http://www.boost.org/LICENSE_1_0.txt)

#ifndef BOOST_XPRESSIVE_DETAIL_CORE_MATCHER_ACTION_MATCHER_HPP_EAN_10_04_2005
#define BOOST_XPRESSIVE_DETAIL_CORE_MATCHER_ACTION_MATCHER_HPP_EAN_10_04_2005

// MS compatible compilers support #pragma once
#if defined(_MSC_VER) && (_MSC_VER >= 1020)
# pragma once
#endif

#include <boost/config.hpp>
#include <boost/version.hpp>
#include <boost/ref.hpp>
#include <boost/assert.hpp>
#include <boost/mpl/if.hpp>
#include <boost/throw_exception.hpp>
#include <boost/type_traits/is_const.hpp>
#include <boost/type_traits/remove_reference.hpp>
#include <boost/xpressive/detail/detail_fwd.hpp>
#include <boost/xpressive/detail/core/quant_style.hpp>
#include <boost/xpressive/detail/core/action.hpp>
#include <boost/xpressive/detail/core/state.hpp>
#include <boost/xpressive/proto/proto.hpp>
#include <boost/xpressive/proto/context.hpp>
#include <boost/xpressive/match_results.hpp> // for type_info_less
#include <boost/xpressive/detail/static/transforms/as_action.hpp> // for 'read_attr'
#if BOOST_VERSION >= 103500
# include <boost/xpressive/proto/fusion.hpp>
# include <boost/fusion/include/transform_view.hpp>
# include <boost/fusion/include/invoke.hpp>
# include <boost/fusion/include/push_front.hpp>
# include <boost/fusion/include/pop_front.hpp>
#endif

#if BOOST_MSVC
#pragma warning(push)
#pragma warning(disable : 4510) // default constructor could not be generated
#pragma warning(disable : 4512) // assignment operator could not be generated
#pragma warning(disable : 4610) // can never be instantiated - user defined constructor required
#endif

namespace boost { namespace xpressive { namespace detail
{

    #if BOOST_VERSION >= 103500
    struct DataMember
      : proto::mem_ptr<proto::_, proto::terminal<proto::_> >
    {};

    template<typename Expr, long N>
    struct child_
      : remove_reference<typename mpl::if_<
            is_const<Expr>
          , typename proto::result_of::arg_c<Expr, N>::const_reference
          , typename proto::result_of::arg_c<Expr, N>::reference
        >::type>
    {};

    ///////////////////////////////////////////////////////////////////////////////
    // mem_ptr_eval
    //  Rewrites expressions of the form x->*foo(a) into foo(x, a) and then
    //  evaluates them.
    template<typename Expr, typename Context, bool IsDataMember = proto::matches<Expr, DataMember>::value>
    struct mem_ptr_eval
    {
        typedef typename child_<Expr, 0>::type left_type;
        typedef typename child_<Expr, 1>::type right_type;

        typedef
            typename proto::result_of::arg<
                typename proto::result_of::arg_c<right_type, 0>::type
            >::type
        function_type;

        typedef
            fusion::transform_view<
                typename fusion::result_of::push_front<
                    typename fusion::result_of::pop_front<right_type>::type const
                  , reference_wrapper<left_type>
                >::type const
              , proto::eval_fun<Context>
            >
        evaluated_args;

        typedef
            typename fusion::result_of::invoke<function_type, evaluated_args>::type
        result_type;

        result_type operator()(Expr &expr, Context &ctx) const
        {
            return fusion::invoke<function_type>(
                proto::arg(proto::arg_c<0>(proto::right(expr)))
              , evaluated_args(
                    fusion::push_front(fusion::pop_front(proto::right(expr)), boost::ref(proto::left(expr)))
                  , proto::eval_fun<Context>(ctx)
                )
            );
        }
    };

    ///////////////////////////////////////////////////////////////////////////////
    // mem_ptr_eval
    //  Rewrites expressions of the form x->*foo into foo(x) and then
    //  evaluates them.
    template<typename Expr, typename Context>
    struct mem_ptr_eval<Expr, Context, true>
    {
        typedef typename child_<Expr, 0>::type left_type;
        typedef typename child_<Expr, 1>::type right_type;

        typedef
            typename proto::result_of::arg<right_type>::type
        function_type;

        typedef typename boost::result_of<
            function_type(typename proto::result_of::eval<left_type, Context>::type)
        >::type result_type;

        result_type operator()(Expr &expr, Context &ctx) const
        {
            return proto::arg(proto::right(expr))(
                proto::eval(proto::left(expr), ctx)
            );
        }
    };
    #endif

    struct attr_with_default_tag
    {};

    template<typename T>
    struct opt;

    ///////////////////////////////////////////////////////////////////////////////
    // action_context
    //
    struct action_context
    {
        explicit action_context(action_args_type *action_args)
          : action_args_(action_args)
        {}

        action_args_type const &args() const
        {
            return *this->action_args_;
        }

        // eval_terminal
        template<typename Expr, typename Arg>
        struct eval_terminal
          : proto::default_eval<Expr, action_context const>
        {};

        template<typename Expr, typename Arg>
        struct eval_terminal<Expr, reference_wrapper<Arg> >
        {
            typedef Arg &result_type;
            result_type operator()(Expr &expr, action_context const &) const
            {
                return proto::arg(expr).get();
            }
        };

        template<typename Expr, typename Arg>
        struct eval_terminal<Expr, opt<Arg> >
        {
            typedef Arg const &result_type;
            result_type operator()(Expr &expr, action_context const &) const
            {
                return proto::arg(expr);
            }
        };

        template<typename Expr, typename Type, typename Int>
        struct eval_terminal<Expr, action_arg<Type, Int> >
        {
            typedef typename action_arg<Type, Int>::reference result_type;
            result_type operator()(Expr &expr, action_context const &ctx) const
            {
                action_args_type::const_iterator where_ = ctx.args().find(&typeid(proto::arg(expr)));
                if(where_ == ctx.args().end())
                {
                    boost::throw_exception(
                        regex_error(
                            regex_constants::error_badarg
                          , "An argument to an action was unspecified"
                        )
                    );
                }
                return proto::arg(expr).cast(where_->second);
            }
        };

        // eval
        template<typename Expr, typename Tag = typename Expr::proto_tag>
        struct eval
          : proto::default_eval<Expr, action_context const>
        {};

        template<typename Expr>
        struct eval<Expr, proto::tag::terminal>
          : eval_terminal<Expr, typename proto::result_of::arg<Expr>::type>
        {};

        // Evaluate attributes like a1|42
        template<typename Expr>
        struct eval<Expr, attr_with_default_tag>
        {
            typedef
                typename proto::result_of::arg<
                    typename proto::result_of::left<
                        typename proto::result_of::arg<
                            Expr
                        >::type
                    >::type
                >::type
            temp_type;

            typedef typename temp_type::type result_type;

            result_type operator ()(Expr const &expr, action_context const &ctx) const
            {
                return proto::arg(proto::left(proto::arg(expr))).t_
                    ? *proto::arg(proto::left(proto::arg(expr))).t_
                    :  proto::eval(proto::right(proto::arg(expr)), ctx);
            }
        };

        #if BOOST_VERSION >= 103500
        template<typename Expr>
        struct eval<Expr, proto::tag::mem_ptr>
          : mem_ptr_eval<Expr, action_context const>
        {};
        #endif

    private:
        action_args_type *action_args_;