[squeak-dev] Re: intersect: when intsersects: is false

Nicolas Cellier nicolas.cellier.aka.nice at gmail.com
Sun Jun 20 19:02:04 UTC 2010

2010/6/20 Louis LaBrunda <Lou at keystone-software.com>:
> On Sun, 20 Jun 2010 11:07:23 +0200, Joachim Geidel
> <joachim.geidel at onlinehome.de> wrote:
>>One could just
>>leave it as it is, because the precondition for answering a "correct"
>>rectangle is that the receiver and the argument intersect. If they don't, the
>>answer is undefined, which means that whatever is answered is correct in a
>>mathematical sense.
> I urge some caution here.  If "whatever is answered is correct in a
> mathematical sense" is true then returning any rectangle like (100 at 100)
> corner: (150 at 150) would be correct, clearly that is not the case.  In
> Smalltalk, nil is undefined, nil is probably the "correct" answer.

Yes, this is tempting.
However from a pragmatic point of view that would mean that:
- either every call must be protected with an intersects: test or (...
intersect ...) ifNil: [...]
- or UndefinedObject must understand Rectangle protocol
Answering an empty rectangle seems more simple with this respect.


> -----------------------------------------------------------
> Louis LaBrunda
> Keystone Software Corp.
> SkypeMe callto://PhotonDemon
> mailto:Lou at Keystone-Software.com http://www.Keystone-Software.com

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