carfield.com.hk

AndExp.java

2004-03-24T16:00:00Z

BooleanConstant.java

2004-03-24T16:00:00Z

BooleanExp.java

2004-03-24T16:00:00Z

BooleanInterpretation.java

2004-03-24T16:00:00Z

package examples.interpreter.aspectj;

/* -*- Mode: Java; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * This file is part of the design patterns project at UBC
 *
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * either http://www.mozilla.org/MPL/ or http://aspectj.org/MPL/.
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is ca.ubc.cs.spl.patterns.
 *
 * Contributor(s): 
 */

/**
 * Attaches implementations of <code>replace(String, BooleanExp)<code> and
 * <code>copy()</code> methods to all concrete <code>BooleanExp</code>s. 
 *
 * The very nature of the interpreter pattern introduces coupling between all
 * participants. Unfortunately, removeing the pattern code from the 
 * participants does not work as nicely here as with other patterns. The
 * reason is that the roles are defining, i.e., each participant's 
 * functionality is determined (only) by its role. Removing pattern
 * specific code into an aspect would leave the Expressions etc.
 * empty and would make the aspect a monolithic module. 
 *
 * However, it is still possible to augment or change the behaviour of the
 * system without changing all participant classes. To show this, we 
 * assumed that <code>BooleanExp.replace(String, BooleanExp)</code> and
 * <code>BooleanExp.copy()</code> were added later. The code for these
 * methods is placed in the aspect, so that other classes did not have to
 * change (we only changed the interface, but even that was not necessary).
 *
 * In general, however, this pattern does not lend itself nicely to 
 * aspectification.
 *
 * @author Jan Hannemann
 * @author Gregor Kiczales
 * @version 1.0, 05/13/02
 * 
 * @see BooleanExp
 */

public aspect BooleanInterpretation {
 
// AndExp

 /**
 * Replaces a variable with an expression. Has no effect.
 *
 * @param name the name of the variable
 * @param exp the expression to replace the variable
 * @returns a copy of this expression with the variable replaced
 */

	public BooleanExp AndExp.replace(String name, BooleanExp exp) {
		return new AndExp(op1.replace(name, exp), op2.replace(name,exp));
	}
		
 /**
 * Copies this expression
 *
 * @returns the copied expression
 */
 
	public BooleanExp AndExp.copy() {
		return new AndExp(op1.copy(), op2.copy());
	} 

// BooleanConstant

 /**
 * Replaces a variable with an expression. Has no effect.
 *
 * @param name the name of the variable
 * @param exp the expression to replace the variable
 * @returns a copy of this expression with the variable replaced
 */

	public BooleanExp BooleanConstant.replace(String name, BooleanExp exp) {
		return exp; // ???
	}
	
 /**
 * Copies this expression
 *
 * @returns the copied expression
 */
 
	public BooleanExp BooleanConstant.copy() {
		return new BooleanConstant(value);
	}

// OrExp
	
 /**
 * Replaces a variable with an expression. Has no effect.
 *
 * @param name the name of the variable
 * @param exp the expression to replace the variable
 * @returns a copy of this expression with the variable replaced
 */

	public BooleanExp OrExp.replace(String name, BooleanExp exp) {
		return new OrExp(op1.replace(name, exp), op2.replace(name,exp));
	}
		
 /**
 * Copies this expression
 *
 * @returns the copied expression
 */
 
	public BooleanExp OrExp.copy() {
		return new OrExp(op1.copy(), op2.copy());
	}
	
// VariableExp

 /**
 * Replaces a variable with an expression. Has no effect.
 *
 * @param name the name of the variable
 * @param exp the expression to replace the variable
 * @returns a copy of this expression with the variable replaced
 */

	public BooleanExp VariableExp.replace(String name, BooleanExp exp) {
		if (name.equals(this.name)) {
			return exp.copy();
		} else {
			return new VariableExp(this.name);
		}
	}
	
 /**
 * Copies this expression
 *
 * @returns the copied expression
 */
 
	public BooleanExp VariableExp.copy() {
		return new VariableExp(name);
	}

// NotExp

	
 /**
 * Replaces a variable with an expression. Has no effect.
 *
 * @param name the name of the variable
 * @param exp the expression to replace the variable
 * @returns a copy of this expression with the variable replaced
 */

	public BooleanExp NotExp.replace(String name, BooleanExp exp) {
		return new NotExp(this.exp.replace(name, exp));
	}
		
 /**
 * Copies this expression
 *
 * @returns the copied expression
 */
 
	public BooleanExp NotExp.copy() {
		return new NotExp(exp.copy());
	}		
}

Context.java

2004-03-24T16:00:00Z

ExpressionException.java

2004-03-24T16:00:00Z

Main.java

2004-03-24T16:00:00Z

package examples.interpreter.aspectj;

/* -*- Mode: Java; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * This file is part of the design patterns project at UBC
 *
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * either http://www.mozilla.org/MPL/ or http://aspectj.org/MPL/.
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is ca.ubc.cs.spl.patterns.
 *
 * Contributor(s): 
 */

/**
 * Implements the driver for the Intepreter design pattern example. 
 *
 * Intent: Given a language, defeine a representation fro its grammar along
 * with an interpreter that uses the representation to interpret sentences
 * in the language.
 *
 * Participating objects are <code>BooleanContant</code>, <code>VariableExp
 * </code>, <code>OrExp</code>, <code>AndExp</code>, and <code>NotExp</code>
 * as Expressions. The AbstractExpression interface is defined 
 * in <code>BooelanExp.
 *
 * This example implements an interpreter for a language of boolean 
 * expressions. As a sample expression, "((true & x) | (y & !x))" is
 * interpreted for all possible boolean values for x and y. After that, 
 * y is replaced by another expression and the whole expression is
 * evaluated again. 
 *
 * This is the AspectJ version.
 *
 * The very nature of this pattern introduces coupling between all 
 * participants. Unfortunately, removeing the pattern code from the 
 * participants does not work as nicely here as with other patterns. The
 * reason is that the roles are defining, i.e., each participant's 
 * functionality is determined (only) by its role. Removing pattern
 * specific code into an aspect would leave the Expressions etc.
 * empty and would make the aspect a monolithic module. 
 *
 * However, it is still possible to augment or change the behaviour of the
 * system without changing all participant classes. To show this, we 
 * assumed that <code>BooleanExp.replace(String, BooleanExp)</code> and
 * <code>BooleanExp.copy()</code> were added later. The code for these
 * methods is placed in the aspect, so that other classes did not have to
 * change.
 *
 * In general, hwever, this pattern does not lend itself nicely to 
 * aspectification.
 *
 * @author Jan Hannemann
 * @author Gregor Kiczales
 * @version 1.0, 05/13/02
 * 
 * @see BooleanExp
 */

public class Main {

 /** 
 * Assigns boolean values to two <code>VariableExp</code>s and evaluates
 * an expression in the given context.
 *
 * @param x a boolean variable expression
 * @param xValue the value to assign to x
 * @param y another boolean variable expression
 * @param yValue the value to assign to y
 * @param context the context to evaluate the expression in
 * @param exp the expression to evaluate
 */

	private static void assignAndEvaluate( VariableExp x, boolean xValue,
						VariableExp y, boolean yValue,
						Context context, BooleanExp exp) {
		context.assign(x, xValue);
		context.assign(y, yValue);
		boolean result = exp.evaluate(context);
		System.out.println("The result for (x="+xValue+", y="+yValue+") is: "+result);
	}

 /**
 * Implements the driver for the Intepreter design pattern example. 
 *
 * This example implements an interpreter for a language of boolean 
 * expressions. As a sample expression, "((true & x) | (y & !x))" is
 * interpreted for all possible boolean values for x and y. After that, 
 * y is replaced by another expression and the whole expression is
 * evaluated again. 
 *
 * @args command-line parameters, unused.
 */

	public static void main(String[] args) {
		BooleanExp exp = null;
		Context context = new Context();
		
		VariableExp x = new VariableExp("X");
		VariableExp y = new VariableExp("Y");		
		
		exp = new OrExp(new AndExp(new BooleanConstant(true), x), 
					 new AndExp(y, new NotExp(x)));
		
		System.out.println("Testing Expr: ((true & x) | (y & !x))");			 

		assignAndEvaluate(x, false, y, false, context, exp);
		assignAndEvaluate(x, false, y, true, context, exp);
		assignAndEvaluate(x, true, y, false, context, exp);
		assignAndEvaluate(x, true, y, true, context, exp);
		
		VariableExp z = new VariableExp("Z");
		NotExp notZ = new NotExp(z);
		
		BooleanExp replacement = exp.replace("Y", notZ);
		context.assign(z, false);
		boolean result = replacement.evaluate(context);

		System.out.println("The result for the replacement is: "+result);
	}
}

NotExp.java

2004-03-24T16:00:00Z

OrExp.java

2004-03-24T16:00:00Z

VariableExp.java

2004-03-24T16:00:00Z

files.lst

2004-03-24T16:00:00Z