TwoIntSet.hs

   1 module TwoIntSet where
   2
   3 import Data.Set
   4
   5 newtype Two a = Two (a,a) deriving (Show, Ord)
   6 type TwoIntSet = Set (Two Int)
   7 instance (Eq a) => Eq (Two a) where
   8   (Two x) == (Two y) = x == y || swap x == y where
   9     swap (n,m) = (m,n)
  10