/*
 *  JFLAP - Formal Languages and Automata Package
 * 
 * 
 *  Susan H. Rodger
 *  Computer Science Department
 *  Duke University
 *  August 27, 2009

 *  Copyright (c) 2002-2009
 *  All rights reserved.

 *  JFLAP is open source software. Please see the LICENSE for terms.
 *
 */





package pumping.reg;

import pumping.*;

/**
 * The regular pumping lemma for <i>L</i> = {<i>a<sup>n</sup></i> 
 * : <i>n</i> is even}.
 * 
 * @author Jinghui Lim & Chris Morgan
 */
public class AnEven extends RegularPumpingLemma 
{
    public String getTitle() 
    {
        return "a^n : n is even";
    }

    public String getHTMLTitle() 
    {
        return "<i>a<sup>n</sup></i> : <i>n</i> is even";
    }
    
    public void setDescription()
    {
    	partitionIsValid = true;
    	explanation = "Because this is a regular language, a valid decomposition exists.  If <i>m</i> " + GREATER_OR_EQ +" 2, " +
    			"the <i>y</i> value \"aa\" will always pump the string.";
    }

    protected void chooseW() 
    {
        if(getM() % 2 == 0)
            w = pumpString("a", getM());
        else
            w = pumpString("a", getM() + 1);
    }

    public void chooseI() 
    {
        i = LemmaMath.flipCoin();
    }

    protected void setRange() 
    {
        myRange = new int[]{2, 18};
    }
    
    public void chooseDecomposition()
    {
    	setDecomposition(new int[] {0, 2});
    }
    
    /**
     * Checks if the pumped string is in the language.
     * 
     * @return <code>true</code> if it is, <code>false</code> otherwise
     */
    public boolean isInLang(String s)
    {
    	String temp;
    	char[] list = new char[]{'a'};
    	if (LemmaMath.otherCharactersFound(s, list))
    		return false;
    	
    	if (s.length() == 0)
    		temp = createPumpedString();
    	else
    		temp = s;    	    	
	    return temp.length() % 2 == 0;
    }
}