Error 1066 - drag isn't a function.

Question

I have the following
1) Main.as - a document class
2) main.fla - the document with a circle
3) Drag.as - with the drag code
drag isn't a function is thrown. That means that main.as can't access the custom drag function but how is that possible if
it's public and in the same folder?
Thanks in advance.
MAIN.as
package {
    import flash.display.*;
    import flash.events.*;
    import Drag;
    public class Main extends MovieClip
        public function Main():void
            circle.drag(); //this is how you implement a method NOT Drag(circle);
DRAG.as
package
   import flash.display.*
   import flash.events.*;
   public class Drag extends MovieClip{
      public var clip:MovieClip = new MovieClip();
      public function Drag(){
      public function drag ():void {
           this.addEventListener(MouseEvent.MOUSE_DOWN, onMouseDownF);// we use this to indicate the object (class instance) that invoked (called) it.
           this.addEventListener(MouseEvent.MOUSE_UP, onMouseUpF);
      private function onMouseDownF(e:Event):void{
         this.startDrag()
      private function onMouseUpF(e:Event):void{
         this.stopDrag();

Answer 1

Hi - I created a new class called Circle which extends Dra class. This way down the line I can add more stuff to Circle Class to make it more specific.
I took circle mc off the timeline (which I know should never have been done anyway - but I was trying to test code quickly and got muddled).
circle now has a proper instance name in the as3 properites panel of Circle.
Everything works perfectly now - is the code below perfect now?
Cheers for the help - this made it very clear for me exactly how to instantiate mcs and how to give them functionality.
package {
    import flash.display.*;
    import flash.events.*;
    public class Main extends MovieClip {
        public var circle:Circle=new Circle;
        //public var circle:Drag=new Drag; //Also works obviously but down the line I want to make more specific additions to Circle class.
        public function Main():void {
            circle.drag();//this is how you implement a method NOT Drag(circle);
            addChild(circle);