The only reason I'd normally expect to have an empty constructor would be
for reflection. To that end, should it have a setComparator/getComparator
methods?
Hen
On Tue, 19 Mar 2002, Morgan Delagrange wrote:
> Do we need an empty constructor? If it does not produce desirable
> behaviour, why not can it?
>
> ----- Original Message -----
> From: "Henri Yandell" <[EMAIL PROTECTED]>
> To: "Jakarta Commons Developers List" <[EMAIL PROTECTED]>
> Sent: Tuesday, March 19, 2002 11:11 AM
> Subject: Re: [collections] ReverseComparator
>
>
> >
> > Functionality wise, I feel that Michael's proposed change is a negative
> > move. However he is absolutely right in all of his points. The current -1
> > does break the Comparator contract, the -1* is unnecessary coding, making
> > the constructor take ComparableComparator is then no different from
> > reverseOrder, and the name then does make more sense as InverseComparator.
> >
> > It's like a stack of dominoes :) Each point seems not necessarily true
> > until you realise each one leads to the next. So I'm:
> >
> > +1 on removing the -1*.
> > +1 on killing the current empty constructor.
> > +0 on using ComparableComparator which simulates reverseOrder
> functionality.
> > It feels bad to replicate this, but we need an empty constructor.
> > +0 on the name of the class. It does behave more as an InverseComparator
> > from a mathematical point of view (which I share), but Reverse does
> > seem more readable.
> >
> > Hen
> >
> >
> > On Tue, 19 Mar 2002, Morgan Delagrange wrote:
> >
> > > Michael suggested that the no-op constructor essentially behave like
> this:
> > >
> > > ReverseComparator() {
> > > this(ComparableComparator.getInstance());
> > > }
> > >
> > > What do you think, Hen? Do you think that is preferable, or do you
> prefer
> > > your initial behaviour (reversing the List).
> > >
> > >
> > > ----- Original Message -----
> > > From: "Henri Yandell" <[EMAIL PROTECTED]>
> > > To: "Jakarta Commons Developers List" <[EMAIL PROTECTED]>
> > > Sent: Tuesday, March 19, 2002 7:50 AM
> > > Subject: Re: [collections] ReverseComparator
> > >
> > >
> > > >
> > > > I'm happy with the name Inverse as it is more what the comparator
> does.
> > > > Reverse makes it easier to see how it can be used for one case, but
> will
> > > > hide other meanings.
> > > >
> > > > Why does this exist over Collections.reverseOrder? Because the Sun
> version
> > > > is limited. Why can I only reverse Comparables? Really there should be
> a
> > > > Collections.reverseOrder(Comparator) as well.
> > > >
> > > > Hen
> > > >
> > > > > I agree that reverse is common terminology when sorting, but I
> disagree
> > > > > that sorting is intrinsicly what a comparator does. While sorting is
> > > > > probably the most common use-case for comparators, the comparator
> itself
> > > > > does not do any sorting. It compares objects and returns a
> negative,
> > > zero
> > > > > value, or positive result. It doesn't rearrange, reverse, order, or
> > > > > "sort". It just compares two objects. This particular comparator
> > > > > "inverses" the result of the compare to be a positive, zero value,
> or
> > > > > negative result (respectively). I use "inverse" here in its
> > > mathematical
> > > > > sense of inverting the result, since that's all this comparator is
> > > doing.
> > > > >
> > > > > I'm not going to argue this anymore though. I've changed my
> position --
> > > > > why is this class even included in commons when the JDK provides a
> > > > > reverse/inverse comparator already? @see Collections.reverseOrder()
> > > > >
> > > > > regards,
> > > > > michael
> > > > >
> > > > > > "Michael A. Smith" wrote:
> > > > > > >[snip]
> > > > > > > Additionally, I think that "InverseComparator" is a more
> appropriate
> > > name,
> > > > > > > as "inverse" has a more direct meaning (to me at least).
> Inverse
> > > has the
> > > > > > > mathematical meaning of the opposite sign which is exactly what
> this
> > > > > > > comparator does. Reverse, on the other hand, implies switching
> the
> > > order
> > > > > > > of something, the comparator isn't really switching the order
> > > (although a
> > > > > > > collection using the comparator may be "reversed" if it uses the
> > > "inverse"
> > > > > > > comparator).
> > > > > > >
> > > > > > > Thoughts?
> > > > > > >[snip]
> > > > > >
> > > > > >
> > > > >
> > > > >
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