Good evening everyone, My program reads:
module Boom where
import Control.Monad.State
type SucParser s = StateT [s] []
newtype WithUnit s a = WithUnit (SucParser s (a, ()))
foo :: SucParser s [s] foo = get
bar :: WithUnit s [s] bar = WithUnit get
The compiler complains: Boom.hs:13:0: Couldn't match expected type `([s], ())' against inferred type `[s]' When using functional dependencies to combine MonadState s (StateT s m), arising from the instance declaration at <no location info> MonadState ([s], ()) (StateT [s] []), arising from a use of `get' at Boom.hs:13:15-17 When generalising the type(s) for `bar' I'm wondering if I'm making a silly mistake or if there's something less trivial going on here. Could someone please explain the error and give a hint on how to fix it? Thanks much. :-) Martijn.