Re: LSP Was: Mixing OO and DB
From: S Perryman <q_at_q.com>
Date: Fri, 22 Feb 2008 14:43:22 +0000
Message-ID: <fpmn2j$va9$1_at_aioe.org>
}
Date: Fri, 22 Feb 2008 14:43:22 +0000
Message-ID: <fpmn2j$va9$1_at_aioe.org>
Bob Badour wrote:
> S Perryman wrote:
BB> In that case, I can only conclude you are an ignorant fool because BB> D&D responded to L&W showing a computational model where Circle is BB> indeed a subtype of Ellipse.
>> I can only conclude that you are an immense fool, for making claims
>> about what people can or cannot do, with no context info to base your
>> claim
>> on (someone with nominal intelligence would IMHO at the very least
>> challenge me to provide the demonstration - YMMV of course) .
> The Third Manifesto. Cure your ignorance and read it.
Immense fool + 1.
Have it (1st edition) . Read it. LOL.
Just to show this one is past its bedtime ...
Here is the apocrypthal Circle/Ellipse problem as would be specified in Liskov/Wing notions :
type Ellipse
{
focusA ; focusB ; invariant : focusA > 0 AND focusB > 0 focusA(A) ; post: focusA = A AND focusB = OLD.focusB}
type Circle
{
radius ; focusA ; focusB ; invariant : radius > 0 invariant : radius = focusA invariant : focusA = focusB focusA(A) ; radius(R) ; post: radius = R
}
Circle is not a Liskov/Wing subtype of Ellipse.
Regards,
Steven Perryman
Received on Fri Feb 22 2008 - 15:43:22 CET