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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: subprogram must not be deeper than access type
Date: Tue, 27 Sep 2011 09:52:09 +0200
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Date: 2011-09-27T09:52:09+02:00
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On Tue, 27 Sep 2011 07:50:54 +0200, J-P. Rosen wrote:

> Le 26/09/2011 21:30, Dmitry A. Kazakov a �crit :
>> I'd like to have anonymous types in record components. It is annoying not
>> to be able to write:
>> 
>>    type Foo is record
>>        Nested : record
>>           end record;
>>        List : array (...) of ...;
>>    end record;
>> 
> "Annoying to write" was never an issue in Ada, where we favor ease of
> reading over ease of writing.

Forward type declarations of types used only for components (and BTW, for
generic instances) are very annoying especially for reading.

> If your Nested component represents a
> logical entity of your problem domain, it deserves a name (i.e. a type).
> And what could you do with this component? Without a type name, no
> subprogram could operate on it.

It is meant only to have large record types structured. E.g.

   type Buffer_Implementation (Size : Positive) is record
      Position : record
            In_Index : ...;
            Out_Index : ...;
              ...
         end record;
      Consumer_Notification : record
            ...  
         end record;
      Data : array (1..Size) of Octet;
      ...

No special meaning other than grouping other components.

Compare it with declare-begin-end blocks they too have no names and have no
identifiable counterpart in the domain, just an implementation detail.

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