please read our papers!

Stef

On May 16, 2008, at 10:52 AM, Ryan Mitchley wrote:

>
> I am genuinely curious to see a simple example that clearly  
> demonstrates the
> advantages of traits.
>
> It is my perception (or misperception) that traits are an attempt  
> (perhaps
> unknowingly) to bring multiple inheritance into the language. As I  
> see it,
> this confuses
> Y Is-A X (i.e. Y subclasses X)
> with
> Y Has-A-Part X (i.e. Y has a member variable / subpart / trait X)
>
> I've seen this in GUI toolkits - e.g. someone has a Bitmap class and a
> ClickableArea class. They want to make a Button - i.e. something  
> that has
> both Bitmap and ClickableArea traits. So they create Button by  
> inheriting
> from both Bitmap and ClickableArea classes (usually C++). The better
> solution is to say that Button has both Bitmap and ClickableArea  
> parts (i.e.
> member variables). This confusion becomes ridiculously clear if we  
> attempt
> to create e.g. a Human class by inheriting from Eye, Leg, Arm etc.  
> There is
> very likely much confusion between all of the members that get  
> dragged in
> and try to compete with each other.
>
> So, if I have a mistaken view of traits, I would in all honesty love  
> to see
> an example that shows this to me clearly.
>
> I have a strong view that software should be designed with a very  
> high view
> of orthogonality. I will often reject non-orthogonal approaches in  
> my own
> software without much thought, simply because I have been down that  
> road
> before and seen the trouble that ensues. That's why I would suggest  
> that
> traits should be rejected IFF they turn out to be a non-orthogonal  
> design
> (i.e. their utility is duplicated by e.g. member variables). I am  
> not yet
> convinced one way or the other.
>
> -- 
> View this message in context: http://www.nabble.com/-squeak-dev--My-view-on-Traits-tp17257352p17270291.html
> Sent from the Squeak - Dev mailing list archive at Nabble.com.
>
>
>