Hal Daume III hdaume@ISI.EDU
Fri, 15 Nov 2002 12:51:35 -0800 (PST)

One work-around is to define something like:

  instance Ord e => Ord (Set e) where
    compare a b = compare (setToList a) (setToList b)

should work fine and shouldn't be too inefficient (I asked a similar
question a while back about FiniteMap, upon which Set is built).

 - Hal

Hal Daume III

 "Computer science is no more about computers    |
  than astronomy is about telescopes." -Dijkstra |

On Fri, 15 Nov 2002, Mark T.B. Carroll wrote:

> Am I right in thinking that sets of sets don't really work with GHC's
> Data.Set because "Set a" things aren't instances of Ord? How should I do
> sets of sets with it?
> (e.g. Set.mkSet [Set.unitSet 1] gives "No instance for (Ord (Set a))")
> -- Mark
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