mapnik/include/comparison.hh

/* This file is part of Mapnik (c++ mapping toolkit)
 * Copyright (C) 2005 Artem Pavlenko
 *
 * Mapnik is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

//$Id$

#ifndef COMPARISON_HH
#define COMPARISON_HH


#include "filter.hh"
#include "expression.hh"
#include "attribute.hh"

namespace mapnik
{   
    template <typename T>  
    struct greater_than
    {
	bool operator() (T const& left, T const& right) const
	{
	    return left > right;
	}
    };

    template <typename T>  
    struct greater_than_or_equal
    {
	bool operator() (T const& left, T const& right) const
	{
	    return left >= right;
	}
    };
    template <typename T>  
    struct less_than
    {
	bool operator() (T const& left, T const& right) const
	{
	    return left < right;
	}
    };
    template <typename T>  
    struct less_than_or_equal
    {
	bool operator() (T const& left, T const& right) const
	{
	    return left <= right;
	}
    };
    template <typename T>  
    struct equals
    {
	bool operator() (T const& left, T const& right) const
	{
	    return left == right;
	}
    };
    
    template <typename T>  
    struct not_equals
    {
	bool operator() (T const& left, T const& right) const
	{
	    return left != right;
	}
    };
    
    template <typename FeatureT,typename Op>
    struct compare_filter : public filter<FeatureT>
    {
	compare_filter(expression<FeatureT> const& left,
		       expression<FeatureT> const& right)
	    : filter<FeatureT>(),
	      left_(left.clone()), right_(right.clone()) {}

	compare_filter(compare_filter const& other)
	    : filter<FeatureT>(),
	      left_(other.left_->clone()),right_(other.right_->clone()) {}
	
	bool pass(const FeatureT& feature) const
	{
	    return Op()(left_->get_value(feature),right_->get_value(feature));     
	}
	void accept(filter_visitor<FeatureT>& v)
	{
	    left_->accept(v);
	    right_->accept(v);
	    v.visit(*this);
	}
	filter<FeatureT>* clone() const
	{
	    return new compare_filter<FeatureT,Op>(*this);
	}
	virtual ~compare_filter() 
	{
	    delete left_;
	    delete right_;
	}
    private:
	expression<FeatureT>* left_;
	expression<FeatureT>* right_;
    };
}

#endif //COMPARISON_HH