These functions have their arguments reversed when compare to e.g. Map For example Data.HashTable.lookuphttp://haskell.org/ghc/docs/latest/html/libraries/base/Data-HashTable.html#v... :: HashTablehttp://haskell.org/ghc/docs/latest/html/libraries/base/Data-HashTable.html#t... key val -> key -> IOhttp://haskell.org/ghc/docs/latest/html/libraries/base/System-IO.html#t%3AIO (Maybehttp://haskell.org/ghc/docs/latest/html/libraries/base/Data-Maybe.html#t%3AM... val) Data.Map.lookuphttp://hackage.haskell.org/packages/archive/containers/0.2.0.0/doc/html/Data... :: Ordhttp://hackage.haskell.org/packages/archive/base/4.0.0.0/doc/html/Data-Ord.h... key => key -> Maphttp://hackage.haskell.org/packages/archive/containers/0.2.0.0/doc/html/Data... key val -> Maybehttp://hackage.haskell.org/packages/archive/base/4.0.0.0/doc/html/Data-Maybe... val I find this a bit odd. Is this by design?