import java.awt.*;			// for Polygon

public abstract class Ch15_1 // demonstrate the creation of an abstract class, this class will represent a generic function f that
{							// can be used to generate the x,y coordinates that the function computes, that is y=f(x)

	protected Polygon p=new Polygon();	// instance datum to be inherited 
	
	public Ch15_1() {					// no arg constructor causes the Polygon p to get values
		drawFunction();
	}

	public void drawFunction() {		// method to compute the polygon by generating f(x) values for x between -100 and +100
		for(int x=-100;x<=100;x++)
			p.addPoint(x+200,200-(int)f(x));	// we call the function f, which will be defined in each child
	}
	
	public abstract double f(double x);		// abstract method needs to be implemented in child classes
	
	public Polygon getPoly() {return p;}	// accessor to get the polygon
}