Distance Between Point and Line (optimized)

/**
Original function by Pieter Iserbyt:
http://local.wasp.uwa.edu.au/~pbourke/geometry/pointline/DistancePoint.java
from Paul Bourke's website:
http://local.wasp.uwa.edu.au/~pbourke/geometry/pointline/
*/
function pointToLineDist(x1:Number, y1:Number, x2:Number, y2:Number,x3:Number, y3:Number):Number {
	var dx:Number=x2-x1;
	var dy:Number=y2-y1;
	if (dx==0&&dy==0) {
		x2+=1;
		y2+=1;
		dx=dy=1;
	}
	var u:Number = ((x3 - x1) * dx + (y3 - y1) * dy) / (dx * dx + dy * dy);

	var closestX:Number;
	var closestY:Number;
	if (u<0) {
		closestX=x1;
		closestY=y1;
	} else if (u > 1) {
		closestX=x2;
		closestY=y2;
	} else {
		closestX=x1+u*dx;
		closestY=y1+u*dy;
	}
	dx=closestX-x3;
	dy=closestY-y3;
	return Math.sqrt(dx * dx +  dy * dy);
}

/**
Test out the function
*/

var dotA:Sprite = dot(100, 100);
var dotB:Sprite = dot(200, 200);
var dotC:Sprite = dot(150, 100, 0x0000FF);
var txt:TextField = TextField(dotC.addChild(new TextField()));
with(txt) x = 5, y = 5, autoSize = "left", selectable = false, mouseEnabled = false;

addEventListener(Event.ENTER_FRAME, onLoop);
function onLoop(evt:Event):void {
	graphics.clear();
	graphics.lineStyle(0,0x000000);
	graphics.moveTo(dotA.x, dotA.y);
    graphics.lineTo(dotB.x, dotB.y);
	txt.text = pointToLineDist(dotA.x, dotA.y, dotB.x, dotB.y, dotC.x, dotC.y).toFixed(2);
}

// draggable dot
function dot(xp:Number, yp:Number, col:uint = 0xFF0000, rad:Number=4):Sprite {
    var s:Sprite = Sprite(addChild(new Sprite));
    s.x = xp;
    s.y = yp;
    with(s.graphics) beginFill(col), drawCircle(0,0,rad);
    s.buttonMode = true;
    s.addEventListener(MouseEvent.MOUSE_DOWN, onDrag);
    return s;
}
function onDrag(evt:MouseEvent):void { evt.currentTarget.startDrag() }
stage.addEventListener(MouseEvent.MOUSE_UP, onUp);
function onUp(evt:MouseEvent):void{stopDrag() }

This is the same as yesterdays post about the distance between a point and a line segment. I just took a few minutes to optimize the function – it runs close to 3X faster now. For more info see yesterdays post.