Re: Negative float problem

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Wed, 02 Nov 2005 10:04:21 +0100, Maciej Sobczak wrote:

> Dmitry A. Kazakov wrote:
> 
>> package A is
>>    type Foo is ...;
>>    function "+" (Left, Right : Foo)  return Foo;
>> end A;
>> -------------------
>> package A.B is
>>    X : Foo;
>>    function "+" (Left, Right : Foo)  return Foo;
>> end A.B;
>> ------------------
>> with A.B;
>> ...
>> A.B.X + A.B.X  -- BOOOOM!
> 
> With ADL, I would expect it to call A."+".

Which perfectly illustrates why there should be no such thing as ADL.
Exactly to prevent making the above legal with the meaning A."+".

> This means that some program, 
> which is not legal without ADL, would be legal with ADL in the language.
> 
> (If your point is that any language feature can seem obscure when shown 
> in obscure examples, then I completely agree.)

No. The point is that the language should maintain views properly. That is
(here I agree with Robert Duff):

If you see A of T, then you also see T.
If you see T then you also see its primitive operations.
[ and one additional point from me: maybe there should be non-primitive
operations allowed in specifications! ]

Another question is how this language design principle should be mapped
into name spaces, public and private views etc. But to me one thing is
clear, kludges like ADL is not the answer.

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