import java.awt.*;
import java.awt.event.*;

public abstract class FunctionPlotter extends Frame {

   int yvalues[];
   static final int xdisp = 20;
   static final int ydisp = 20;
   static final int maxy = 400;
   static final int samples = 100;
   static final int extraspace = 20;

   public FunctionPlotter() {
      yvalues = new int[samples];
      setSize(samples+xdisp+extraspace, maxy+ydisp+extraspace);
      for(int x = 0; x<100; x++)
         yvalues[x] = 0;
      // exits when window gets closed
      addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
			});
   }
   
   public void paint(Graphics g) {
      g.drawLine(xdisp, extraspace+extraspace, xdisp, maxy+ydisp);
      g.drawLine(0, maxy-ydisp, samples+xdisp, maxy-ydisp);
      g.setColor(Color.blue);
      for(int x = 0; x < 99; x++)
         g.drawLine(xdisp+x,maxy-ydisp-yvalues[x],
                    xdisp+(x+1),maxy-ydisp-yvalues[x+1]);
   }

   public void plot() {
     for(int x = 0; x < 100; x++)
         yvalues[x] = (int) Math.round(f(1.0*x));
      show();
   }

 
   public abstract double f(double x);

}