Hi, I'm working on understanding the state monad, and I got stumped pretty much right away. When I run the following script (with instances copied verbatim from http://www.haskell.org/all_about_monads/html/statemonad.html ) #!/usr/bin/env runhaskell \begin{code} {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies #-} import Control.Monad.State(Monad, MonadState(..)) newtype State s a = State { runState :: (s -> (a,s)) } instance Monad (State s) where return a = State $ \s -> (a,s) (State x) >>= f = State $ \s -> let (v,s') = x s in runState (f v) s' instance MonadState (State s) s where get = State $ \s -> (s,s) put s = State $ \_ -> ((),s) main :: IO () main = putStrLn "hello" \end{code} It fails with: statemonadtest.lhs:11:20: `State s' is not applied to enough type arguments Expected kind `*', but `State s' has kind `* -> *' In the instance declaration for `MonadState (State s) s' Can you see what I'm doing wrong? I must be making a really basic mistake but I'm not sure what it is. Thanks, Keith -- keithsheppard.name