Duplicate functions

in many languages you can define multiple functions with the same name but different parameters for instance:

show(x:Number,y:Number){
point = new Point(x,y);
}

show(){
point = new Point(10,10);
}

in as3 I get this Error:

1021: Duplicate function definition.

how can I do this in as3? (if I even will be able to do this)