From: wtanksle at dolphin.openprojects.net (William Tanksley)
Date: Thu, 29 Apr 1999 23:11:38 GMT
Subject: Python IS slow ! [was] Re: Python too slow for real world
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On Wed, 28 Apr 1999 19:19:57 -0700, Al Christians wrote:
>> >Actually, isn't Eiffel's type system famous for being full of holes?

>> I'm familiar with the covariance/contravariance argument, but I've never
>> before heard anyone say anything about Eiffel being full of holes.  What
>> problems have you heard of?

>I think it's called changing availability by type, or some such.

No, CAT is a feature of any object system (never a bug).

>It is
>possible to delete a feature in a descendant class, leaving a hole in
>polymorphic calls through the base class.  

This would be true, but feature deletion is not used for public
interfaces.  It's mainly used when you're treating inheritance as though
it were 'import' (certainly a major weakness of Eiffel).  It's true that
you can abuse it by making that feature deletion public, but the type
system could just as easily forbid you from doing any such thing (I have
no idea whether it does).

I think you were talking about Meyer's insistance on covariance.  I would
call that _one_ hole, albeit a strange one.  It's certainly not enough to
condemn it as full of holes -- its type system is in other ways quite
robust.

>Al

-- 
-William "Billy" Tanksley
"But you shall not escape my iambics."
           -- Gaius Valerius Catullus




