/*
 *  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>b<sup>n</sup></i> : <i>n</i> &#8805; 0}.
 * 
 * @author Jinghui Lim & Chris Morgan
 */
public class AnBn extends RegularPumpingLemma 
{
    public String getTitle()
    {
        return "a^n b^n : n >= 0";
    }
    
    public String getHTMLTitle() 
    {
        return "<i>a<sup>n</sup>b<sup>n</sup></i> : <i>n</i> " + GREATER_OR_EQ + " 0";
    }    
    
    public void setDescription()
    {
    	partitionIsValid = false;
    	explanation = "For any <i>m</i> value, a possible value for <i>w</i> is \"a<sup><i>m</i></sup>" +
		"b<sup><i>m</i></sup>\".  The <i>y</i> value thus would be a multiple of \"a\".  " +
		"For any <i>i</i> "+ NOT_EQUAL +" 1, n<sub>a</sub> "+ NOT_EQUAL +" n<sub>b</sub>, giving a string " +
		"which is not in the language.  Thus, the language is not regular.";	
    }
    
    protected void chooseW() 
    {
        w = pumpString("a", m) + pumpString("b", m);
    }
    
    public void chooseI()
    {
        i = LemmaMath.flipCoin();
    }
    
    protected void setRange()
    {
        myRange = new int[]{4, 18};
    }
    
    public boolean isInLang(String s)
    {
    	int a, b;
    	char[] list = new char[]{'a','b'};
    	if (LemmaMath.isMixture(s, list))
    		return false;
    	
    	a = LemmaMath.countInstances(s, 'a');
    	b = LemmaMath.countInstances(s, 'b');
    	if (a==b)
    		return true;    	    	
        return false;
    }
}