package lab.art;

/**
 * This class represents the average expression.
 * 
 * @author Franck van Breugel
 */
public class Average extends BinaryExpression 
{
    /**
     * Initializes this average expression with the given two subexpressions.
     * 
     * @param first the first subexpression.
     * @pre. first != null
     * @param second the second subexpression.
     * @pre. second != null
     */
    public Average(Expression first, Expression second) 
    {
	super(first, second);
    }

    /**
     * Evaluates this average 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 average expression at the given x- and y-coordinate.
     */
    public double evaluate(double x, double y)
    {
	BinaryOperator average = new AverageOperator();
	return super.evaluate(x, y, average);
    }
    
    /**
     * Returns a string representation of this average expression.
     * The string consists of "average(" followed by the string representation
     * of the first subexpression, followed by ", " followed by the 
     * string representation of the second subexpression, followed by ")".
     * 
     * @return string representation of this average expression.
     */
    public String toString()
    {
	String pattern = "average(%s, %s)";
	return super.toString(pattern);
    }
}