[Haskell-cafe] [Newbie] Quest for inheritance

Gracjan Polak gracjan at acchsh.com
Tue Jun 7 04:13:54 EDT 2005

Ralf Lammel wrote:
>>Cédric Paternotte wrote:
>> > 5. With this :
>> >
>>Gracjan Polak wrote:
>>I've been thinking about slight generalization of this lately. Here are
>>my semi-backed thoughts as of now.
> I should have mentioned 
> http://homepages.cwi.nl/~ralf/OOHaskell/src/PoorMens2/
> (again *not* using OOHaskell)

 From the quick skim of code:
.?. -- apply function to upcast object
.!. -- apply modification function to upcast object and substitute 
returned value (new object), basically update

Is there any description avaliable what is PoorMens2 all about?

> A more general and preliminary observation:
> the entire approach is potentially more about
> object *composition* (and perhaps delegation) 
> rather than inheritance. Many OO evangelists 
> consider inheritance as a concept that was used
> too much in early OO times, while object composition
> is often more appropriate and flexible. So one *might*
> say that this approach does not encode a Java-inheritance
> solution but it does an inheritance-to-object-composition
> migration on the fly. So what Gracjan calls "Inherits"
> (and I call subtyping or substitution) is perhaps more a
> "delegates".

Yes, I agree with this statement. The OP question was: how to simulate 
inheritance in Haskell? One of the answers: using delegation :)

> Ralf


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