import java.awt.*;
import java.applet.Applet;
import java.awt.event.*;        

public class roundoff extends Applet implements ActionListener{
	// Applet for iteration of the Baker-map. Stefan Emet 1998.
	Label Label_X_0;
	TextField TextField_X_0;	
	Button Button_Next, Button_Clear;
	double X_t, X_0=0.6;
	int t=0, x_position;
	boolean CLEAR=true,NEW=true;

public void init(){
	add(Label_X_0=new Label("X(0):"));
	add(TextField_X_0=new TextField(""+X_0,3));
	add(Button_Next=new Button("Iterate"));		
	add(Button_Clear=new Button("Clear"));		
}
public void paint(Graphics g){
	// width=400 and height=350
	update(g);
}
public void update(Graphics g){
	if (CLEAR){
		x_position=0;		
		g.setColor(Color.white);
		g.fillRect(0,100,399,224);
		g.setColor(Color.black);
		g.drawRect(0,100,399,224);		
		g.drawRect(8,33,345,40);
		g.drawString("X(t+1) = B( X(t) ), where t=0,1,2, ...",15,50);
		g.drawString("B(x) = ",195,53);
		g.drawString("2 x ,  if x is in [0 , 1/2]",230,47);
		g.drawString("2 x - 1 ,  if x is in ]1/2, 1]",230,63);
		g.setColor(Color.red);
		g.drawString("Choose a startpoint X(0) from the interval [0,1]. Press Iterate-button to iterate B(X(0)).",5,95);
		g.setColor(Color.black);
		if (NEW){						
			X_t=X_0;
			NEW=false;
		}
		CLEAR=false;
	}
	if (t>0){
		if (t%32==0){
			CLEAR=true;
		}
		else if ((t-1)%16==0){
			x_position=x_position==10 ? 200:10;
		}
		X_t=B(X_t);
		g.drawString("X("+t+") = "+X_t,x_position,115+((t-1)%16)*13);
	}
}
public double B(double x){
	return x<=(double)1/2 ? 2*x:2*x-1;
}
public void actionPerformed(ActionEvent e){
	Object source=e.getSource();
	double in;

	in=Double.valueOf(TextField_X_0.getText()).doubleValue();
	if (in != X_0){
		X_0=in;
		CLEAR=NEW=true;
		t=0;
	}	
	if (source.equals(Button_Next)){
		t++;
		repaint();
	}
	else if (source.equals(Button_Clear)){
		CLEAR=NEW=true;
		t=0;
		repaint();
	}
}

}// class roundoff