Hello everyone, Please help me compile the program without the -XFlexibleContexts extension. I don't understand the "Non type-variable argument" error message and googling does not shed any light on the problem. Any help is appreciated. % ghc --version The Glorious Glasgow Haskell Compilation System, version 7.10.3 % ghc orfest.hs orfest.hs:6:1: Non type-variable argument in the constraint: AM.MArray a (t, t, t, [i]) m (Use FlexibleContexts to permit this) When checking that ‘go’ has the inferred type go :: forall (m :: * -> *) t t1 t2 t3 (a :: * -> * -> *) i. (Read t, AM.Ix i, AM.MArray a (t, t1, t2, [i]) m) => a i (t, t1, t2, [i]) -> [[Char]] -> t3 -> i -> m (t3, i) This works: % ghc orfest.hs -XFlexibleContexts Regards, Orfest