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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: using an Ada.Container as a private type
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Date: Thu, 3 Apr 2008 18:02:48 +0200
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Date: 2008-04-03T18:02:48+02:00
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On Thu, 3 Apr 2008 08:29:28 -0700 (PDT), Graham wrote:

> Hi,
>     I'm writing a little financial application. I want to model a
> stream of payments made at arbitrary periods (the periods are positive
> numbers; they might be actual dates later on).
> 
> I think I want to declare this:
> 
> 
> type Payment_Stream is private;
> 
> procedure Add_To_Payment_Stream(
>             stream : in out Payment_Stream;
>             period :  Positive;
>             amount : Money );
> 
> ......
> 
> and then privately declare the payment stream as an Ordered Map, like:
> 
> private
> 
>    package Payment_Stream_Package is new Ada.Containers.Ordered_Maps(
>       Element_Type => Money,
>       Key_Type => Positive );
> 
>    type Payment_Stream is new Payment_Stream_Package.Map;

   type Payment_Stream is new Payment_Stream_Package.Map with null record;

> but I can't do this. Gnat complains that "type derived from tagged
> type must have extension".

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de