inheriting from array class

hi, I want to create my array class which extends the functionality of the base array.

I wrote something like this:

package {

    public class my_array extends Array {

// (...)

    public function my_array(_long:int) {

            // (...)

            super(_long);

        }

    } // class

} // package

in other words, I have to call the super constructor, and since when I declare a new array I specify the lenght of the array, I pass the length of the array to the super constructor.

Nothing wrong so far, but when I try to use my new array, like this:

var test:my_array = new my_array(10);

test[0] = 1;

I get this error:

ReferenceError: Error #1056: Cannot create property 0 on my_array.

    at rob1_fla::MainTimeline/frame1()

then I replaced the 'super' line in the constructor of my class with this one:

this = super(_long);

and now I get this one:

1050: Cannot assign to a non-reference value.

so how do I extend the array class, so I can use the indexes of my new array class?

tnx