[Haskell] duplicate elements in Data.Set

Walter Moreira gwallter at gmail.com
Sat Jan 21 20:00:04 EST 2006

Please, discard this question. It was my fault, the compare function
was a partial order instead of a total order.


Jean-Philippe Bernardy wrote:
> I'd say your compare function isn't transitive.
> If you can tell it's well behaved, and if you can send me even your
> complicated example, I'll look into it.
> Cheers,
> JP.
> On 1/21/06, Walter Moreira <gwallter at gmail.com> wrote:
>> Hello list. Are there situations where a set can contain duplicate
>> elements?
>> I have a newtype and it is an instance of 'Eq' via the 'compare' method,
>> and it is also an instance of 'Ord'. After some Data.Set operations
>> with sets of that type I get a set which contains two elements which
>> compare equal. What am I doing wrong?
>> The function 'Set.valid' returns 'False' when applied to the set. I
>> use the function 'Set.fromList' sometimes. Is it supposed to always
>> yield a valid set? or it may depend on the order or equality?
>> Sorry the question is a little vague. When I try to construct small
>> examples the problem disappear.
>> Thanks,
>> Walter
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