6. My module applies Data.Set.null (s :: Set a), and null (xs :: [a]).
Why ghc reports of the clash with GHC.List.null ? Is GHC.List same as old List library module? Should I write import GHC.List (genericLength, null) instead of import List (genericLength) ?
As the documentation reads: This module is intended to be imported qualified, to avoid name clashes with Prelude http://www.haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html functions. eg. import Data.Set as Set So, you should write: import qualified Data./x/ as /y/ Now, no name clashes will occur. However, you will have to write /y/.null to access null in /x/, for example: import qualified Data.Set as Set if (Set.null ...) then ... else ... Regards, Robert