[486] in java-interest
Re- Array Subclassing and I
daemon@ATHENA.MIT.EDU (Warren Harris)
Fri Jun 23 21:02:13 1995
Date: 23 Jun 1995 17:18:31 -0700
From: "Warren Harris" <warren_harris@genmagic.com>
To: "p d" <pdoane@pcnet.com>, "j i" <java-interest@java.sun.com>
Subject: Re: Array Subclassing and IncompatibleTypeException
> From: pdoane@pcnet.com (Patrick Doane)
> Date: Fri, 23 Jun 1995 10:04:12 -0400
> Subject: Re: Array Subclassing and IncompatibleTypeException
>
> >Recently Bill Joy, Guy Steel, David Ungar and Ole Madsen have been
> >evaluating the Java language and they have pointed out that our =
current
> >array type system may not be the optimal choice. As it turns we only
> >allow co-variant argument types on array types and not on class types.
> >We are working on a proposal which, in the future, allows us to =
express
> >arrays as parameterized types without the requirement for co-variant =
arguments.
> >I'll let you know the result of this discussion.
>
> I'm interested in exactly what this means. I've had very little =
formal
> Computer Science training and the words here are confusing me. Any help
> would be appreciated in understanding this.
>
> Patrick
Patrick,
I wrote a paper a while back that might help explain co- and =
contravariant
arguments to methods. It's called "Contravariance for the rest of us", in =
JOOP
(Journal of Object-Oriented Programming) Nov/Dec 1991. It explains the =
phenomenon
in terms of C++. It also discusses some of the research we were doing at =
HP Labs
back then to design a more expressive language.
Warren
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