<? /* $Id: Restaurant_Arithmetic.php,v 1.2 2005/04/04 20:37:14 david Exp $ */

//  http://davidmintz.org/php_course/7/assignment.txt

// Write a class called MyRestaurantCalculator that implements the following interface.
// Save it along with the following code in a file called MyRestaurantCalculator.php
// Upload it as the Week 7 assignment.

interface Restaurant_Arithmetic {
	
	/* returns the sum of X and Y */
	function add($x,$y)	;
	
	/* returns the absolute difference between $x and $y 
	that is, $object->subtract(2,3) and $object->(3,2) should
	both return 1. see the abs function for help.
	*/
	function subtract($x,$y);
	
	
	/* returns the product of x and y rounded to the nearest cent */
	function multiply($x,$y);
	
	
	/* returns x divided by y rounded to the nearest cent
	if y is zero just return null before you divide*/
	function divide($x,$y);
	
	
	/* returns $amount plus the amount times $percent_tax_rate/100
	round it off to the nearest cent (see the round() function for help)
	in other words, $object->addSalesTaxTo(113.43,8.25) should 
	return 123.03 */
	function addSalesTaxTo($amount,$percent);
	
	
	/*  identical with behavior of addTipTo(), so make 
	one an alias of the other. e.g.,
	function x($arg) { return $this->other_func($arg) ;}*/
	function addTipTo($amount,$percent);
	
	
	/* returns the sales tax on $amount at $percent percent
	rounded to the nearest cent	*/
	function computeSalesTaxOn($amount,$percent);
}
?>