Re: Universal type in Ada

[Preben Randhol <randhol+cla@pvv.org>]

zw <zw@cs.man.ac.uk> wrote on 15/06/2005 (13:11) :
> Hi, I am trying to create a Universal type in Ada such as "Object" in
> Java so that I could define a function that returns a value in this
> Universal type, then I could lower-cast value in this type to its
> specific type such as String, Float or any user-defined types. Because
> in Java if a method returns an Object, it could be casted to any other
> types that are subtypes of Object. Is there a Universal type in Ada?
> Could anyone tell me how to create such types in Ada, please?

Why would you want to do something like this? Generally you don't want
to use subtypes over types as you loose the advantage of the Ada type
checking...

Remember that in Ada one can have:

     function Method (Some_Input : Input_Type) return Integer;
     function Method (Some_Input : Input_Type) return Float;
     function Method (Some_Input : Input_Type) return String;

And do:

   Number : Integer := Method (Input);
   Height : Float   := Method (Input);
   Text   : String  := Method (Input);

then the correct function will be called depending on return type.

Please explain what you want to do and we can give better hints to do it
in more Ada-wise ways.

Preben