On Friday 24 June 2005 14:28, Andreas Rossberg wrote:
Ralf Lammel wrote:
I would like to add a peer-reviewed clear reference
to the OOHaskell paper about the red herring that you mention.
I don't have such a reference. May I kindly ask you to offer
a few for selection?
Off-hand, I recall a paper by Martin Odersky and the Scala people
discussing their approach to the Expression Problem, and a related
paper by Jacques Garrigue, where he proposes to solve it using
OCaml's polymorphic variants. Both should be easy to dig up with
Google, and probably contain further pointers.
Inspired by this post I read some of the available papers on Scala
(among them the above).
I find Scala very, very interesting.
However, I am quite curious how the inventors of Scala managed to to
write 100's of dense pages of papers, citing influences from 10's of
other languages...
...and at the same time completely fail to even once mention Eiffel,
which shares a lot of interesting features with Scala. The paper An
overview of the Scala Programming Language lists allogether 10
Authors. Have really none of those 10 authors ever heard of Eiffel and
its famous attitude of we are using multiple inheritance more often
than loops?
Ok, Eiffel has a few holes in its type-system, doesn't naturally
integrate with Java/.Net, and doesn't support XML directly. And Eiffel
does not support deferred types in class definitions.
But: IIRC, Eiffel was the first OO-language that almost completely
solved the multiple-inheritance problem, providing solutions very
similar to ones in Scala. For instance, mixin-type inheritance is
easily possible in Eiffel. Also, Eiffel provides the same kind of
automatic replacement of deferred (expected) methods and attributes
with concrete (implemented) ones.
In a few places, Eiffel is even more general. For instance, in Eiffel
you can even inherit two concrete methods with the same name. In order
to resolve the name conflict you just rename one of them in your
derived class. Furthermore, Eiffel does not distinguish between class
and trait (although maybe the distinction is a good idea) without
placing any restrictions on classes. Another nice feature of Eiffel is
that access can be restricted in a very fine grained way, i.e. for each
single method (or group of methods) you can give a list of classes that
are allowed to call this method.
Ben
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