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Subject: Re: On packages hierarchy
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Date: 2014-07-28T17:24:58-06:00
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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...

     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