On 13/10/13 21:42, AntC wrote:
Niklas Hambüchen
writes: In sets, the order does not matter, while for nub it does.
Let's be careful here!. Niklas, when you say "order", do you mean: * the _ordering_ from the Ord instance? Or * the relative sequence of elements in the list?
... the fact that Set is used inside my proposed ordNub implementation is a detail not visible to the caller.
If you use the Set library, that fact may be very visible! Because Set re-sequences the whole list, as per its Ord instance.
But List.nub preserves the list sequence (except for omitting duplicates).
I mean *exactly* what you say here. ordNub behaves has the same behaviour as nub, while (Set.toList . Set.fromList) doesn't.
[BTW I am still less than convinced that overall a Set-based ordNub is significantly more efficient. I suspect it depends on how big is your list.]
What do you mean? ordNub is clearly in a different complexity class, and the benchmarks that I provided show not only this, but also that ordNub is *always* faster than nub, even for singleton lists.