How To Represent Class Wide Constants

["Anthony E. Glover" <aglover@elmco.com>]

What is the best approach for representing class wide constants
within Ada95? Specifically, I have classes that contain values that
are read in from a data file and remain unchanged throught the
life of the program. They are the same for all objects of the class.
Also, in some cases, sub-classes need to be able to override the
values of the parent class with their own set of values. Currently
I am implementing them as primitive functions of the class and
overriding the function within the sub-class. I also default the
object to a null record that way I can retrieve the value without
having to pass an object. See below:

package MyClass is

    type MyClass_Type is .....

    function Null_Object return MyClass_Type;

    function Constant1( Object : MyClass_Type := Null_Object ) return Float;

etc...

I can then invoke MyClass.Constant1 to retrieve the value for that constant.

Can this been done in a better way?

Thanks for any help.
Tony