On 19 May 2009, at 09:06, Ryan Ingram wrote:
This is a common problem with trying to use do-notation; there are some cases where you can't make the object an instance of Monad. The same problem holds for Data.Set; you'd can write setBind :: Ord b => Set a -> (a -> Set b) -> Set b setBind m f = unions (map f $ toList m) but there is no way to use setBind for a definition of >>=
You can use a continuation trick. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
