variabletermimpl.java

Mandarax是一个规则引擎的纯Java实现。它支持多类型的事实和基于反映的规则

package org.mandarax.reference;

/*
 * Copyright (C) 1999-2004 <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</a>
 *
 * 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 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
import org.mandarax.kernel.*;
import org.mandarax.util.TermIterator;
import java.util.*;

/**
 * Reference implementation for variable terms.
 * @author <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</A>
 * @version 3.4 <7 March 05>
 * @since 1.1
 * Prova re-integration modifications
 * @author <A HREF="mailto:[e-mail]">Alex Kozlenkov</A>
 * @version 3.4 <7 March 05>
 */
public class VariableTermImpl extends LObject implements VariableTerm {

	private String name = null;
	private Class  type = null;

	/** Cache the string representation for optimized debugging. */
	private transient String cachedToString = null;

	/**
	 * Create a new instance with the name and the type passed as parameter.
	 */
	public VariableTermImpl() {
		super ();
	}

	/**
	 * Create a new instance with the name and the type passed as parameter.
	 * @param n the name of the variable
	 * @param t the type of the variable
	 */
	VariableTermImpl(String n, Class t) {
		super ();
		setName (n);
		setType (t);
	}
	/**
	 * Get a (trivial) term iterator for the subterms.
	 * @return an iterator for all sub terms
	 */
	public TermIterator allSubterms() {
		Term[] t = { this };

		return new TermIterator (t);
	}
	/**
	 * Apply a replacement to a term.
	 * @return the term resulting from applying the replacement
	 * @param r the replacement
	 */
	public Term apply(Replacement r) {
		if(r.original.sameAs (this)) {
			return r.replacement;
		} else {
			return this;
		}
	}

	public void getAllSubtermsA( List result ) {
		result.add( this );
	}

	public void getAllSubtermsA( List result, boolean left ) {
		result.add( this );
	}

	public boolean getAllSubtermsB( List result, Iterator aux ) {
		Object t = ConstantTermImpl.nextNotNull( aux );
		if( t!=null ) {
			result.add(this);
			return (t instanceof VariableTermImpl) && (this==t);
		}
		return false;
	}

	public boolean getAllSubtermsB( List result, Iterator aux, boolean left ) {
		Object t = ConstantTermImpl.nextNotNull( aux );
		if( t!=null ) {
			result.add(this);
			return (t instanceof VariableTermImpl) && (this==t);
		}
		return false;
	}

	/**
	 * Indicates whether the term containes variables.
	 * @return true
	 */
	public boolean containsVariables() {
		return true;
	}

	/**
	 * Indicates whether the term contains the provided variable term.
	 * @return true if the term contains the variable term provided, false otherwise
	 * @param var a variable term
	 */
	public boolean containsVariable( VariableTerm var ) {
		return this==var;
	}

	/**
	 * Indicates whether the objects are equal.
	 * @return true if the objects are equal, false otherwise
	 * @param t the object to compare this object with
	 */
	public boolean equals(Object t) {
		if( !(t instanceof org.mandarax.kernel.VariableTerm)) {
			return false;
		}

		return type.equals (((VariableTerm) t).getType ())
			   && name.equals (((VariableTerm) t).getName ());
	}
	/**
	 * Get all subterms as array.
	 * @return an array of terms only containing this object
	 */
	public Term[] getAllSubterms() {
		Term[] t = { this };

		return t;
	}
	/**
	 * Get the name of the variable.
	 * @return the name of the variable
	 */
	public String getName() {
		return name;
	}
	/**
	 * Get the type of the variable.
	 * @return the term type
	 */
	public Class getType() {
		return type;
	}
	/**
	 * Returns the hashcode of the object.
	 * @return the hash value
	 */
	public int hashCode() {
		return type.hashCode () ^ name.hashCode () * 31;
	}
	/**
	 * Indicates whether the term is compound.
	 * @return false
	 */
	public boolean isCompound() {
		return false;
	}
	/**
	 * Indicates whether the term is constant.
	 * @return false
	 */
	public boolean isConstant() {
		return false;
	}
	/**
	 * Indicates whether the object (usually a term or a clause set) can be performed
	 * using the java semantics. Variable terms do not support the java semantics!
	 * @return false
	 */
	public boolean isExecutable() {
		return false;
	}
	/**
	 * Indicates whether the term is a variable.
	 * @return true
	 */
	public boolean isVariable() {
		return true;
	}
	/**
	 * Resolve a constant term. This is trivial: just
	 * throw an excpetion (variables cannot be resolved).
	 * @param session a session object
	 * @return the result of resolving the term
	 * @throws java.lang.UnsupportedOperationException
	 * @throws java.lang.IllegalArgumentException
	 */
	public Object resolve(Session session) throws UnsupportedOperationException, IllegalArgumentException {
		throw new UnsupportedOperationException ();
	}

//	/**
//	 * Resolve a constant term. This is trivial: just
//	 * throw an excpetion (variables cannot be resolved).
//	 * @return the result of resolving the term
//	 * @throws java.lang.UnsupportedOperationException
//	 * @throws java.lang.IllegalArgumentException
//	 */
//	public Object resolve()
//			throws UnsupportedOperationException, IllegalArgumentException {
//		throw new UnsupportedOperationException ();
//	}

	/**
	 * Indicates whether the object is the same as the parameter.
	 * @return true if the both objects are the same
	 * @param t another term
	 */
	public boolean sameAs(Term t) {
		if( !(t instanceof org.mandarax.kernel.VariableTerm)) {
			return false;
		}

		return type.equals (((VariableTerm) t).getType ())
			   && name.equals (((VariableTerm) t).getName ());
	}
	/**
	 * Set a name.
	 * @param n the new name
	 */
	public void setName(String n) {
		name = n;
	}
	/**
	 * Set a type.
	 * @param t the type
	 */
	public void setType(Class t) {
		type = t;
	}
	/**
	 * Convert the receiver to a string.
	 * @return the string representation of this object
	 */
	public String toString() {
		if (cachedToString == null) {
			StringBuffer buf = new StringBuffer ();

			buf.append ("<");
			buf.append (name);
			buf.append (">");

			cachedToString = new String (buf);
		}
		return cachedToString;
	}
}