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#ifndef _OperatorQuery_h_
#define _OperatorQuery_h_
//
// OperatorQuery.h
//
// OperatorQuery: (abstract class) a query that combines result lists
// returned by other queries kept in an operand list.
// how they are combined is tbd by the concrete classes.
//
// Part of the ht://Dig package <http://www.htdig.org/>
// Copyright (c) 1995-2004 The ht://Dig Group
// For copyright details, see the file COPYING in your distribution
// or the GNU Library General Public License (LGPL) version 2 or later
// <http://www.gnu.org/copyleft/lgpl.html>
//
// $Id: OperatorQuery.h,v 1.4 2004/05/28 13:15:24 lha Exp $
//
//
// for details about the basic architectural pattern see the book:
// Design Patterns, by the infamous GoF
// Interpreter pattern
//
#ifdef HAVE_CONFIG_H
#include "htconfig.h"
#endif
#include "Query.h"
#include "List.h"
// abstract
class OperatorQuery : public Query
{
public:
virtual ~OperatorQuery()
{
operands.Destroy();
}
// add an operand to the operation
void Add(Query *operand)
{
operands.Add(operand);
}
protected:
OperatorQuery() {}
// get results from operands and combine them ad-hoc
virtual ResultList *Evaluate() = 0;
// keyword name of the operation
virtual String OperatorString() const = 0;
// human-readable unparsed string
virtual String GetLogicalWords() const;
// cache index
String GetSignature() const
{ return String("Compound:")+GetLogicalWords(); }
// children query operands
List operands;
};
#endif
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