On 12/3/07, Ross Paterson
But in the case at issue, the proposed Bounded instance is counter-intuitive because the underlying Ord instance is. That Ord instance is an arbitrary choice that is accepted because it allows IntSets to be used as search keys; it makes no sense on its own.
I don't find that to be the case. If you had asked me to independently come up with an ordering on IntSets, the existing ordering is exactly what I would have invented. As I said earlier, lexicographic order is very well known. It's arbitrary, but it's a universally-agreed arbitrary. It's how words are ordered in paper dictionaries, for example. (To be precise, to compare two IntSets, you convert them to lists with toList, then compare the lists with lexicographic order.)