Re: Nil items in NSMutableSet
Re: Nil items in NSMutableSet
- Subject: Re: Nil items in NSMutableSet
- From: Alejandro Rodriguez <email@hidden>
- Date: Tue, 16 Mar 2010 16:58:03 -0400
Thats a very interesting take on the problem. I'm going to look into that. Make sure that isEqual: returns the same both ways. Thanks and I'll let you know how it goes. I can't really reproduce the issue so I won't know if it's fixe but at least I'll test the commutativity of the comparison.
Cheers,
Alejandro
On Mar 16, 2010, at 2:45 PM, Clark Cox wrote:
> On Tue, Mar 16, 2010 at 11:35 AM, Thomas Davie <email@hidden> wrote:
>>> Your code doesn't account for the possibility that the order of
>>> comparison might happen in the other order (i.e. [@"123" isEqual:
>>> object]). I wouldn't be surprised if NSSet is assuming that equality
>>> is transitive (i.e. [a isEqual: b] == [b isEqual: a]).
>>
>> For reference, this property is not transitivity, the transitivity relation is:
>>
>> a -> b ^ b -> c => a -> c (for some relation ->)
>>
>> The one you're looking for is commutativity.
>
> Indeed; must have been echos of my previous life as a C++ programmer
> creeping into the Obj-C part of my brain (in C++, the std::set class
> uses less than, instead of equality, where transitivity is the
> important property, not commutativity).
>
> :)
>
>
>
> --
> Clark S. Cox III
> email@hidden
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