From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,be21015280cacd24
X-Google-Attributes: gid103376,public
From: dweller@dfw.net (David Weller)
Subject: Re: (no subject)
Date: 1996/04/09
Message-ID: <4kecpk$ltg@dfw.dfw.net>#1/1
X-Deja-AN: 147074361
references: <4ke8pk$bua@post.tau.ac.il>
organization: DFWNet -- Public Internet Access
newsgroups: comp.lang.ada
Date: 1996-04-09T00:00:00+00:00
List-Id: <comp.lang.ada>

In article <4ke8pk$bua@post.tau.ac.il> you write:
>I would Like to write an abstract package that will implement Sets in
>two ways, one with list and one with array, I need to declare a base 

This is very similar to how the Booch Components does it...

>type and then derive from it. doe's anybody has something like it 
>or can help me write it.(I don't know how to write the spec for the
>the derived type)
>
>package Sets is 
>
>generic
>   type Set_Element is private;
>
>package Abstract_Sets is
>  
>   type Set is abstract tagged private;
>
> ..[various functions deleted]
>
>private
>   type Set is abstract tagged null record;
>end Abstract_Sets;
>

I think you want:

generic
   type Set_Element is private;  -- or (<>), depending on your preferences
package Sets is
	type Set is abstract tagged private;

	[same functions that you already had...]

private
	type Set is abstract tagged with null record;
end Sets;

then...

generic	-- must have "generic" since parent is a generic
package Sets.List_Based is

	type List_Set is new Set with private;

	[redefinitions of abstract operations]
private
	type List_Set is new Set with record...
end Sets.List_Based;

Similarly for Sets.Array_Based  (or whatever you call them)