From: Pit Capitain <pit@...>
Date: 2001-08-16T20:41:11+09:00
Subject: [ruby-talk:19887] Re: Why not?: Assigning to self

On 16 Aug 2001, at 19:14, Erwan David wrote:

> matz@ruby-lang.org (Yukihiro Matsumoto) writes:
> 
> > In message "[ruby-talk:19867] Re: Why not?: Assigning to self"
> >     on 01/08/16, "Pit Capitain" <pit@capitain.de> writes:
> > 
> > |Take the famous Shape class hierarchy:
> > |
> > |class Shape; ...; end
> > |class Rectangle < Shape; ...; end
> > |class Square < Rectangle; ...; end
> > 
> > I feel you're relying too much on inheritance hierarchy.  In Ruby,
> > it's at best implementation sharing.
> 
> Well that's seems not to me inheritance for me, but definition by
> constraints... And I do not know any language implementing this...
> (IE defining that a square is a rectangle which verifies the
> constraint that width = heigth).

Searching the web for something like rectangle/become/square I 
found a language called cecil, that has so called predicate 
subclasses, which seem to offer this functionality. See 
http://www.cs.washington.edu/research/projects/cecil/cecil/www/ce
cil-home.html

Regards,
Pit