package lab.art;

/**
 * This class represents an expression.
 * 
 * @author Franck van Breugel
 */
public abstract class Expression 
{
    /**
     * Initializes this expression.
     */
    public Expression()
    {
	super();
    }
    
    /**
     * Evaluates this expression at the given x- and y-coordinate.
     * 
     * @param x the x-coordinate.
     * @pre. x >= -1 && x <= 1
     * @param y the y-coordinate.
     * @pre. y >= -1 && y <= 1
     * @return the value of this expression at the given x- and y-coordinate.
     */
    public abstract double evaluate(double x, double y);
}