From: Kristof Bastiaensen <kristof@...>
Date: 2004-08-08T03:16:33+09:00
Subject: Re: Sets are not extensional

On Sun, 08 Aug 2004 00:16:11 +0900, Charles Mills wrote:

> On Aug 7, 2004, at 6:11 AM, Kristof Bastiaensen wrote:
> 
>> Hi,
>>
>> On Fri, 06 Aug 2004 18:08:57 +0000, Csaba Henk wrote:
>>> [snip]
>>> I've read the thread spawned by this post, and now I summarize that
>>> part
>>> of what was written there which is relevant to my original problem, and
>>> wasn't stated there explicitly.
>>>
>>>
>> I think the thread was relevant to your post, since it described what
>> was causing the bug.  The following should solve the problems (but can
>> be very slow for large Hashes/Sets):
>>
>> class Array
>>   def hash
>>     to_a.hash
>>   end
>> end
>>
> I think you mean:
> 
> class Hash
>    def hash
>      to_a.hash
>    end
> end
> 
> -Charlie
> 

I did.  Thanks!

KB

>> Regards,
>> KB
>>
>>> "Set" can be forced to behave extensionally by doing so:
>>>
>>> class Set
>>>   def eql? other
>>>     subset? other and other.subset? self
>>>   end
>>>   def hash
>>>     to_a.hash
>>>   end
>>> end
>>>
>>> -- as it seems to me, Array#uniq uses *both* of eql? and hash methods,
>>> and
>>> to get rid of the (IMHO pathological) behaviour illustrated by the
>>> above
>>> examples, both methods need to be overwritten. Concerning the above
>>> re-implementation of these methods, what I did with "hash" is just a
>>> hack,
>>> of course, I don't claim that it clean or right to do so, it just
>>> something which does the job.
>>
>>
>>