Ticket #2329 (closed bug: wontfix)
Control.Parallel.Strategies: definitions of rnf for most collections are poor
These all perform a lot of consing, which seems rather undesirable. It would be very nice indeed if they could be rebaked in terms of strict left folds. Unfortunately, all of the collections in question seem only to expose non-strict left folds publicly.
instance (NFData k, NFData a) => NFData (Data.Map.Map k a) where rnf = rnf . Data.Map.toList instance NFData a => NFData (Data.Set.Set a) where rnf = rnf . Data.Set.toList instance NFData a => NFData (Data.Tree.Tree a) where rnf (Data.Tree.Node r f) = rnf r `seq` rnf f instance NFData a => NFData (Data.IntMap.IntMap a) where rnf = rnf . Data.IntMap.toList instance NFData Data.IntSet.IntSet where rnf = rnf . Data.IntSet.toList