//Copyright F.Beukers 2001

import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.lang.*;
import java.math.*;


public class bigCollatz extends Applet {

	static BigInteger mindrie = new BigInteger("-3");
	static BigInteger mineen = new BigInteger("-1");
	static BigInteger nul = new BigInteger("0");
	static BigInteger een = new BigInteger("1");
	static BigInteger drie = new BigInteger("3");
	static BigInteger vijf = new BigInteger("5");

	int fontsize=18;
	TextField text = new TextField("0",30);
	TextField vanaf = new TextField("0",4);
	TextField totaan = new TextField("100",4);
	TextArea bord = new TextArea();
	Choice method = new Choice();
	Choice mode = new Choice();
	Choice digits = new Choice();
	Button go = new Button("Go");
	Font myFont = new Font("Dialog",Font.PLAIN,fontsize);

public void init() {
	go.addActionListener(new ActionListener() {
		public void actionPerformed(ActionEvent e) {
			dotheloop();}
			});
	setLayout(new BorderLayout());
	Panel p1 = new Panel();
	Panel p2 = new Panel();
	p1.setBackground(Color.pink);
	p2.setBackground(Color.pink);
	p1.setFont(myFont);
	text.setFont(myFont);
	vanaf.setFont(myFont);
	totaan.setFont(myFont);
//	bord.setFont(myFont);
	method.add("3n+1");
	method.add("3n-1");
	method.add("3n+3");
	method.add("3n+5");
	method.add("5n-3");
	method.add("5n-1");
	method.add("5n+1");
	method.add("5n+3");
	mode.add("long");
	mode.add("short");
	digits.add("decimal");
	digits.add("binary");
	p1.add(new Label("N ="));
	p1.add(text);
	p1.add(go);
	p2.add(new Label("Method:"));
	p2.add(method);
	p2.add(mode);
	p2.add(new Label("    Show from"));
	p2.add(vanaf);
	p2.add(new Label("to"));
	p2.add(totaan);
	p2.add(digits);
	bord.setSize(500,300);
	add("North",p1);
	add("South",p2);
	add("Center",bord);
	repaint();
	}

public void dotheloop() {
	BigInteger m, a=drie, b=een;
	int k, from=0, to=100, c=1, algo=1, radix=10;
	try {from = Integer.parseInt(vanaf.getText().trim());}
	catch(NumberFormatException err) {
		from=0; text.setText("0");
		bord.append("Invalid start encountered\n");return;}
	try {to = Integer.parseInt(totaan.getText().trim());}
	catch(NumberFormatException err) {
		to=0; text.setText("100");
		bord.append("Invalid end encountered\n");return;}
	try {m = new BigInteger(text.getText().trim());}
	catch(NumberFormatException err) {
		m=nul; text.setText("0");
		bord.append("Invalid N encountered\n");return;}
	if(from<0) {bord.append("start must be >=0!\n"); return;}
	if(to<=from) {bord.append("end must be larger than start!\n"); 
		return;}
	if(m.signum()<=0) {bord.append("N must be positive!\n"); return;}
	bord.selectAll();
	bord.replaceRange("",
		bord.getSelectionStart(),bord.getSelectionEnd());
	
	algo = method.getSelectedIndex();
	switch(algo) {
		case 0: a=drie;b=een;break;
		case 1: a=drie;b=mineen;break;
		case 2: a=drie;b=drie;break;
		case 3: a=drie;b=vijf;break;
		case 4: a=vijf;b=mindrie;break;
		case 5: a=vijf;b=mineen;break;
		case 6: a=vijf;b=een;break;
		case 7: a=vijf;b=drie;break;
		}
	algo = mode.getSelectedIndex();
	switch(algo) {
		case 0: c=0; break;
		case 1: c=1; break;
		}
	algo = digits.getSelectedIndex();
	switch(algo) {
		case 0: radix=10;break;
		case 1: radix=2;break;
		}
	for (k=0;k<=to;k++) {
		if (k>=from) {
			bord.append(Integer.toString(k)+" :\t");
			bord.append(m.toString(radix)+"\n");
			}
		if(m.testBit(0)==true) {
			m=m.multiply(a);
			m=m.add(b);
			if(c>0) m=m.shiftRight(1);
			}
		else m=m.shiftRight(1);
		}
	}
		
}