> On Fri, 2009/08/21, Quincey Morris <quinceymor...@earthlink.net> wrote: > From: Quincey Morris <quinceymor...@earthlink.net> > Subject: Re: When do I need to override hash? > To: "cocoa-dev" <cocoa-dev@lists.apple.com> > Date: Friday, 2009 August 21, 00:48 >> On 2009 Aug 20, at 22:05, Jeff Laing wrote: >> Without wanting to keep the thread going forever, >> can I just ask why we would presume this? >> >> In fact, if I were implementing NSDictionary >> I'd assume the reverse, that I was not allowed >> to assume that an objects hash would not change..
>>>>> "If a mutable object is added to a collection >>>>> that uses hash values to determine the >>>>> object’s position in the collection, the >>>>> value returned by the hash method of the >>>>> object must not change while the object >>>>> is in the collection." The impression I get from all this is that * if you do want to change how you hash, you should pull objects out of the collections with the old hash and then add them back in using the new hash. * be careful when choosing a hash scheme; it has to be fast and it has to produce keys that minimize collisions and yet come out the same when you want it to come out the same. _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
