[529] in java-interest
Re: Operator overloading (was: BigInteger class out there?)
daemon@ATHENA.MIT.EDU (Jake Kesinger)
Wed Jun 28 14:34:44 1995
Date: Wed, 28 Jun 1995 10:55:08 -0700 (PDT)
From: Jake Kesinger <jake@blegga.freerange.com>
To: Michael Lorton <mlorton@eshop.com>
Cc: java-interest@java.sun.com
In-Reply-To: <199506281529.IAA09500@eshop.com>
On Wed, 28 Jun 1995, Michael Lorton wrote:
>
> [Greg Wilkins <gregw@ind.tansu.com.au> writes]
>
> then you really need
> a degree in pure maths to work out the group theory for any non-trival
> classes that you want to use these features for.
>
> If it looks like * it needs to act like *, so the group of all your
> classes instances needs to be reflexive, transitive, have a unity
> instance etc. etc.
>
> I disagree here also. If I were writing a Matrix class, I would very
> much like to overload the *. I would certainly NOT want reflexivity,
> since bA != Ab. Moreover, the same argument could apply against
> methods with operator-like names (multiply() or add()).
Two things:
1. Are arithmetical expressions transitive in any programming language?
I seem to remember hearing once that some compilers reserve the
right to re-arrange lines in optimization.
2. No object in Java (to my knowledge) is a group under ``*''.
``*'' certainly isn't invertible (a*0==0), nor is it closed
(MAXINT * 3). Also, is it always true with IEEE floating point
numbers that 1.0*f == f == f*1.0?
Has anyone considered operator methods? i.e. something like
public Complex operator (Complex b)Mult(Complex a);
Which would look like:
Complex x,y,z;
z := x Complex.Mult() y;
or
z := x Mult() y;
--Jake
>
> Any tool can be misused. The question is does the potential cost of
> abuse exceed (or even approach) the benefit of proper use. In the
> case of automatic conversion, I agree with the growing consensus that
> says yes. I am not convinced about operator overloading; group theory
> is not going to convince me.
>
> M.
>
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