package ca.ubc.cs.spl.aspectPatterns.examples.interpreter.java;

/* -*- 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.aspectPatterns.
 * 
 * For more details and the latest version of this code, please see:
 * http://www.cs.ubc.ca/labs/spl/projects/aodps.html
 *
 * Contributor(s):   
 */

/**
 * Implements negation for booleans expressions. This is a concrete boolean
 * <i>NonterminalExpression</i>
 *
 * @author  Jan Hannemann
 * @author  Gregor Kiczales
 * @version 1.1, 02/11/04
 */

public class NotExpression implements BooleanExpression {

    /** 
     * the <i>Expression</i> this <i>Expression</i> negates
     */
     
	protected BooleanExpression exp = null;
	
	/**
	 * Creates a new NOT <i>Expression</i> negating the 
	 * argument <i>Expression</i>   
	 *
	 * @param exp the <i>Expression</i> to negate  
	 */

	public NotExpression(BooleanExpression exp) {
		this.exp = exp;
	}
	
    /**
     * Evaluates this <i>Expression</i> in the given <i>Context</i>
     *
     * @param c the context to evaluate the <i>Expression</i> in
     * @return the boolean value of the <i>Expression</i>
     */

	public boolean evaluate(VariableContext c) {
		return (! exp.evaluate(c)); 
	}
	
    /**
     * Replaces a variable with an <i>Expression</i>
     *
     * @param name the name of the variable
     * @param exp the <i>Expression</i> to replace the variable
     * @return a copy of this <i>Expression</i> with the variable replaced
     */

	public BooleanExpression replace(String name, BooleanExpression exp) {
		return new NotExpression(this.exp.replace(name, exp));
	}
		
    /**
     * Copies this <i>Expression</i>
     *
     * @returns the copied <i>Expression</i>
     */

	public BooleanExpression copy() {
		return new NotExpression(exp.copy());
	}
}