Proposal: Bounded instance for IntSet (ticket #1953)
Stefan O'Rear
stefanor at cox.net
Sun Dec 2 19:23:11 EST 2007
On Sun, Dec 02, 2007 at 04:01:05PM -0800, David Benbennick wrote:
> On 12/2/07, Ross Paterson <ross at soi.city.ac.uk> wrote:
> > These are the minimum and maximum under the Ord instance (also for Set),
> > but what is the intuition behind that ordering?
>
> The order on IntSet is the well-known lexicographic order (see
> http://en.wikipedia.org/wiki/Lexicographical_order). If this proposal
> is accepted, I intend to propose the Bounded instance for Set next
> (Bounded a => Bounded (Set a)).
This contradicts your code, for the maximal element in the lexicographic
order is *not* singleton maxBound, but rather fromList [minBound ..
maxBound].
(The libraries agree with your code but not your explanation...)
Stefan
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