examples/example3.js
function addPoints (x1, y1, x2, y2, cb) {
	var xFinal = x1 + x2;
	var yFinal = y1 + y2;
	cb(xFinal, yFinal);
}
function addPoints (x1, y1, x2, y2, cb) {
	var xFinal = x1 + x2;
	var yFinal = y1 + y2;
	cb(xFinal, yFinal);
}
function addPoints ( x1 , y1 , x2 , y2 , cb ) { var xFinal = x1 + x2 ; var yFinal = y1 + y2 ; cb ( xFinal , yFinal ) ; }
this function takes the sum of two points, and returns the sum of x's and the sum of y's in a callback
this function takes the sum of two points and returns the sum of x s and the sum of y s in a callback