Hi. I'm trying to control the scope within which functions can be used by putting them in a type class. Unfortunately I can't seem to figure out how to get it done. Any advice would be much appreciated. What I want is to start out in a certain scope, which restricts me to using functions in that scope or opening up a subsidiary scope at which point I'm restricted to functions in that scope or opening up an even deeper scope. Hopefully a failed attempt will help explain what I'm trying to achieve... the following has trouble with the inScope{B,C} functions. type AInfo = String type BInfo = String type CInfo = String type BResult = Int type CResult = Char class (Monad m) => WithinA m where askAInfo :: m AInfo class (WithinA m) => WithinB m where askBInfo :: m BInfo class (WithinB m) => WithinC m where askCInfo :: m CInfo class (WithinA m) => ScopeA m where getAInfo :: m AInfo putAInfo :: AInfo -> m () updateAInfo :: BResult -> m () inScopeB :: (ScopeB m2) => m2 BResult -> m BResult class (WithinB m) => ScopeB m where getBInfo :: m BInfo putBInfo :: BInfo -> m () inScopeC :: (ScopeC m2) => m2 CResult -> m CResult class (WithinC m) => ScopeC m where getCInfo :: m CInfo putCInfo :: CInfo -> m () aScoped :: (ScopeA m) => m String aScoped = do bResult <- inScopeB bScoped updateAInfo bResult return "done" bScoped :: (ScopeB m) => m BResult bScoped = do i1 <- b1 i2 <- b2 return (i1 + i2) b1 :: (ScopeB m) => m Int b1 = return 2 b2 :: (ScopeB m) => m Int b2 = inScopeC cScoped >>= return . fromEnum cScoped :: (ScopeC m) => m Char cScoped = return '(' Thanks Daniel