File: query_node.h

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/*
**	SWISH++
**	query_node.h
**
**	Copyright (C) 2004  Paul J. Lucas
**
**	This program 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
**	(at your option) 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#ifndef	query_node_H
#define	query_node_H

// standard
#ifdef	DEBUG_eval_query
#include <iostream>
#endif
#include <new>
#include <vector>

// local
#include "query.h"
#include "simple_pool.h"

//*****************************************************************************
//
// SYNOPSYS
//
	class query_node : public PJL::simple_pool_object<query_node>
//
// DESCRIPTION
//
//	A query_node is the abstract base class for all nodes in a query tree.
//
//*****************************************************************************
{
public:
	class visitor {
		//
		// A visitor is an abstract base class for an object that
		// "visits" nodes in the tree during traversal.
		//
	public:
		virtual ~visitor();
		virtual query_node* operator()( query_node* ) const = 0;
	};

	virtual ~query_node();

	virtual void		eval( search_results& ) = 0;
	virtual query_node*	visit( visitor const& );
#	ifdef DEBUG_eval_query
	virtual std::ostream&	print( std::ostream& ) const = 0;
#	endif
protected:
	query_node() { }
	query_node( pool_type &p ) : pool_object_type( p ) { }
};

//*****************************************************************************
//
// SYNOPSYS
//
	class and_node : public query_node
//
// DESCRIPTION
//
//	An and_node is-a query_node that implements "and" in queries.
//
//*****************************************************************************
{
public:
	typedef std::vector< query_node* > child_node_list;

	typedef child_node_list::iterator iterator;
	typedef child_node_list::const_iterator const_iterator;
	typedef child_node_list::reverse_iterator reverse_iterator;
	typedef child_node_list::const_reverse_iterator const_reverse_iterator;

	and_node( pool_type&, child_node_list& );
	~and_node();

	iterator	begin()		{ return child_nodes_.begin(); }
	const_iterator	begin() const	{ return child_nodes_.begin(); }
	iterator	end()		{ return child_nodes_.end(); }
	const_iterator	end() const	{ return child_nodes_.end(); }
	void		eval( search_results& );
	query_node*	visit( visitor const& );
#	ifdef DEBUG_eval_query
	std::ostream&	print( std::ostream& ) const;
#	endif
protected:
	child_node_list child_nodes_;
};

//*****************************************************************************
//
// SYNOPSYS
//
	class empty_node : public query_node
//
// DESCRIPTION
//
//	An empty_node is-a query_node that is used to represent a leaf node in
//	a query tree that has no search results.
//
//*****************************************************************************
{
public:	//
	// Since we only ever want a single empty_node object to exist, we
	// override operators new and delete.
	//
	void*	operator new( size_t )			{ return &singleton_; }
	void	operator delete( void*, size_t )	{ /* do nothing */ }

	void		eval( search_results& );
#	ifdef DEBUG_eval_query
	std::ostream&	print( std::ostream& ) const;
#	endif
private:
	static empty_node singleton_;
};

#ifdef	FEATURE_word_pos
//*****************************************************************************
//
// SYNOPSYS
//
	class near_node : public query_node
//
// DESCRIPTION
//
//	A near_node is-a query_node that implements "near" in queries.  Unlike
//	all other nodes, the child nodes of a near_node MUST be word_nodes
//	because their word_ranges are used to compute search results.
//
//*****************************************************************************
{
public:
	class distributor : public visitor {
		//
		// A distributor is-a visitor that is used to "distribute" the
		// child nodes of a near_node that are not word_nodes since the
		// child nodes of a near_node MUST be word_nodes.  For example:
		//
		//	cat near (mouse or bird)
		//
		// becomes:
		//
		//	(cat near mouse) or (cat near bird)
		//
	public:
		distributor( query_node *other, bool not_near = false ) :
			other_( other ), not_near_( not_near ) { }

		query_node*	operator()( query_node* ) const;
	private:
		near_node*	make_node(
					pool_type&, query_node*, query_node*
				) const;

		query_node *const other_;
		bool const not_near_;
	};

	near_node( pool_type&, query_node*, query_node* );
	~near_node();

	query_node*	distribute();
	void		eval( search_results& );
	query_node*	left () const { return left_child_ ; }
	query_node*	right() const { return right_child_; }
	query_node*	visit( visitor const& );

#	ifdef DEBUG_eval_query
	std::ostream&	print( std::ostream& ) const;
#	endif
private:
	query_node *const left_child_, *const right_child_;
};

//*****************************************************************************
//
// SYNOPSYS
//
	class not_near_node : public near_node
//
// DESCRIPTION
//
//	A not_near_node is-a near_node that implements "not near" in queries.
//
//*****************************************************************************
{
public:
	not_near_node( pool_type &pool, query_node *left, query_node *right ) :
		near_node( pool, left, right ) { }
	~not_near_node();

	void		eval( search_results& );

#	ifdef DEBUG_eval_query
	std::ostream&	print( std::ostream& ) const;
#	endif
};
#endif	/* FEATURE_word_pos */

//*****************************************************************************
//
// SYNOPSYS
//
	class not_node : public query_node
//
// DESCRIPTION
//
//	A not_node is-a query_node that implements "not" in queries.
//
//*****************************************************************************
{
public:
	not_node( pool_type &p, query_node *child ) :
		query_node( p ), child_( child ) { }
	~not_node();

	query_node*	child() const { return child_; }
	void		eval( search_results& );
	query_node*	visit( visitor const& );
#	ifdef DEBUG_eval_query
	std::ostream&	print( std::ostream& ) const;
#	endif
private:
	query_node *const child_;
};

//*****************************************************************************
//
// SYNOPSYS
//
	class or_node : public query_node
//
// DESCRIPTION
//
//	An or_node is-a query_node that implements "or" in queries.
//
//*****************************************************************************
{
public:
	or_node( pool_type &p, query_node *left, query_node *right ) :
		query_node( p ), left_child_( left ), right_child_( right ) { }
	~or_node();

	void		eval( search_results& );
	query_node*	left () const { return left_child_ ; }
	query_node*	right() const { return right_child_; }
	query_node*	visit( visitor const& );
#	ifdef DEBUG_eval_query
	std::ostream&	print( std::ostream& ) const;
#	endif
private:
	query_node *const left_child_, *const right_child_;
};

//*****************************************************************************
//
// SYNOPSYS
//
	class word_node : public query_node
//
// DESCRIPTION
//
//	A word_node is-a query_node that implements either "word" or "word*"
//	in queries.
//
//*****************************************************************************
{
public:
	word_node( pool_type&, char const*, word_range const&, int );
	~word_node();

	void			eval( search_results& );
	int			meta_id() const	{ return meta_id_; }
	word_range const&	range() const	{ return range_; }
#	ifdef DEBUG_eval_query
	std::ostream&		print( std::ostream& ) const;
#	endif
private:
	char *const word_;
	word_range const range_;
	int const meta_id_;
};

////////// inlines ////////////////////////////////////////////////////////////

#ifdef	FEATURE_word_pos
inline near_node* near_node::distributor::make_node(
	pool_type &pool, query_node *left, query_node *right
) const {
	return not_near_ ?
		new not_near_node( pool, left, right ) :
		new     near_node( pool, left, right ) ;
}
#endif

#endif	/* query_node_H */
/* vim:set noet sw=8 ts=8: */