Hello, A practical question about getting hashing to work. Having used Data.Map before, I wanted to try Data.HashMap.Lazy instead: ---- {-# LANGUAGE DeriveGeneric #-} import Data.HashMap.Lazy as HM import GHC.Generics (Generic) import Data.Hashable data Colour = Red | Green | Blue deriving Generic instance Hashable Colour foo = HM.insert Red ---- The data and its instance definition are directly from the web page https://hackage.haskell.org/package/hashable-1.2.1.0/docs/Data-Hashable.html. However, I det the following error: ---- GHCi, version 7.6.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. [1 of 1] Compiling Main ( htest.hs, interpreted ) htest.hs:13:8: No instance for (hashable-1.1.2.5:Data.Hashable.Hashable Colour) arising from a use of `insert' Possible fix: add an instance declaration for (hashable-1.1.2.5:Data.Hashable.Hashable Colour) In the expression: insert Red In an equation for `foo': foo = insert Red Failed, modules loaded: none. ---- I do not know what is wrong or how I could fix it. Note that my Haskell had originally the older hashable-1.0.0 package, but I cabal-installed this hashable-1.1.2.5 because surfing the net suggested that it would be much better. Could it be the case that the instance goes somehow in the wrong class? -- Matti Nykänen