/home/andreas/src/svn/mapnik/include/mapnik/expression.hpp

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/*****************************************************************************
 * 
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2006 Artem Pavlenko
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 *****************************************************************************/

//$Id$

#ifndef EXPRESSION_HPP
#define EXPRESSION_HPP

#include <mapnik/value.hpp>
#include <mapnik/filter_visitor.hpp>

namespace mapnik {
    template <typename FeatureT> class filter_visitor;
    template <typename FeatureT>
    class expression
    {
    public:
        virtual value get_value(FeatureT const& feature) const=0;
        virtual void accept(filter_visitor<FeatureT>& v)=0;
        virtual expression<FeatureT>* clone() const=0;
        virtual std::string to_string() const=0;
        virtual ~expression() {}
    };

    template <typename FeatureT> 
    class literal : public expression<FeatureT>
    {
    public:
        literal(int val)
            : expression<FeatureT>(),
              value_(val) {}
        literal(double val)
            : expression<FeatureT>(),
              value_(val) {}
        literal(std::wstring const& val)
            : expression<FeatureT>(),
              value_(val) {}
        literal(literal const& other)
            : expression<FeatureT>(),
              value_(other.value_) {}
        
        value get_value(FeatureT const& /*feature*/) const
        {
            return value_;
        }
          
        void accept(filter_visitor<FeatureT>& v)
        {
            v.visit(*this);
        }
          
        expression<FeatureT>* clone() const
        {
            return new literal(*this); 
        }
          
        std::string to_string() const
        {
            return value_.to_expression_string();
        }
        ~literal() {}
    private:
        value value_;
    };
  

    template <typename FeatureT> 
    class property : public expression<FeatureT>
    {
    public:
        property(std::string const& name)
            : expression<FeatureT>(),
              name_(name)
            {}
        
        property(property const& other)
            : expression<FeatureT>(),
              name_(other.name_)
            {}

        value get_value(FeatureT const& feature) const
        {
            return feature[name_];
        }
        void accept(filter_visitor<FeatureT>& v)
        {
            v.visit(*this);
        }
        expression<FeatureT>* clone() const
        {
            return new property(*this); 
        }
        std::string const& name() const
        {
            return name_;
        }

        std::string to_string() const
        {
            return "["+name_+"]";
        }

        ~property() {}

    private:
            std::string name_;
    };
}

#endif //EXPRESSION_HPP

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