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From: Victor Porton <porton@narod.ru>
Newsgroups: comp.lang.ada
Subject: Re: On packages hierarchy
Date: Tue, 29 Jul 2014 15:36:58 +0300
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Date: 2014-07-29T15:36:58+03:00
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Shark8 wrote:

> On 28-Jul-14 10:35, Victor Porton wrote:
>>> Why not just have a single stream type?
>> I want to make an interface to streams of Raptor C library.
>>
>> Because, as you say, we are to have a single stream type, this type
>> should be well-interfaces with that "single" Ada stream class.
>>
>>> >Moreover, Ada's root-stream is abstract, so you can't have objects of
>>> >that type.
>> Well, I mean object of Root_Stream_Type'Class.
> 
> Again, why?
> Your Raptor-stream type /will/ be an concrete-instance of
> Root_stream_type, and a member of its class, won't it? I mean unless I'm
> completely misunderstanding you...

My raptor stream is derived from some my base class.

Due no multiple type inheritance in Ada, it cannot be also derived from 
Root_Stream_Type. So I need a wrapper type.

>      Use Ada.Streams;
>      Type Dave is new Root_Stream_Type with null record;
> 
> 
>      overriding procedure Read
>       (Stream : in out Dave;
>        Item   : out Stream_Element_Array;
>        Last   : out Stream_Element_Offset);
> 
> 
>     procedure Write
>       (Stream : in out Dave;
>        Item   : Stream_Element_Array);
> 
> ---- Implementation:
> 
>   overriding procedure Read
>       (Stream : in out Dave;
>        Item   : out Stream_Element_Array;
>        Last   : out Stream_Element_Offset)
>     is null; -- Replace this with actual implementation.
> 
>   overriding procedure Write
>       (Stream : in out Dave;
>        Item   : Stream_Element_Array)
>     is null; -- Replace this with actual implementation.
> 
> Perhaps reading the first and second posts on this thread will help you
> understand:
> 
> http://computer-programming-forum.com/44-ada/07c6cd94dbb2d6b1.htm
-- 
Victor Porton - http://portonvictor.org