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From: amir@iae.nsk.su (Amir Yantimirov)
Newsgroups: comp.lang.ada
Subject: Re: Imitation is the sincerest form of flattery
Date: 24 Mar 2003 21:48:54 -0800
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message news:<b5nhiq$29oaug$2@ID-77047.news.dfncis.de>...
>Amir Yantimirov wrote:
>> Oops. Sorry. Anyway, the idea is type functionality may be extended
>> freely so it don't have to be specified in type declaration.

> If nothing specified then nothing can be checked at compile time. There are 
> languages like SmallTalk for this, they have their place, but of little 
> interest. Because the real challenge is: to check as much as possible, 
> giving up as little as we can.

Not that. I propose something alike this:

type TFoo = record ... end record;

procedure Bar ( Baz : in out TFoo);
  with TFoo:
    'First = 1;
    'Last = 32;
    [].Read = ReadBits;
    [].Write = WriteBits;
  end with;
begin
  Baz[40] := 0; -- compile error!

> > Fine. But what's the gain? I rarely needs any _polymorphic_ feature
> > for such types above "this type is distinct four-byte thing".
> 
> And what is lost? You need no class-wide objects? Declare them specific!
> 
> BTW, Boolean is an enumeration type, check google, and you'll find periodic 
> discussions in c.l.a concerning "extensionable" enumeration types:
> 
> type Four_State_Logical is new Boolean with (Uncertain, Contradictory);

Different levels of abstraction needs different solutions. So I argue
only that ALL types should be tagged.

Amir Yantimirov
http://www174.pair.com/yamir/programming/