Associated types
type family WriterType (m :: Type -> Type)
Methods
tell :: WriterType m -> m ()Shout to the monad what you want to be heard. The monad carries this packet upwards, merging it if needed (hence the Monoid requirement).
listen :: m a -> m (a, WriterType m)Listen to a monad acting, and return what the monad "said".
pass :: m (a, WriterType m -> WriterType m) -> m aProvide a writer transformer which changes internals of the written object.
Instances10MonadWriter, …
MonadWriter m => MonadWriter (MaybeT m)Defined in monads-tf-0.3.0.1 · Control.Monad.Writer.ClassMonadWriter m => MonadWriter (ExceptT e m)Defined in monads-tf-0.3.0.1 · Control.Monad.Writer.ClassMonadWriter m => MonadWriter (IdentityT m)Defined in monads-tf-0.3.0.1 · Control.Monad.Writer.ClassMonadWriter m => MonadWriter (ReaderT r m)Defined in monads-tf-0.3.0.1 · Control.Monad.Writer.ClassMonadWriter m => MonadWriter (StateT s m)Defined in monads-tf-0.3.0.1 · Control.Monad.Writer.ClassMonadWriter m => MonadWriter (StateT s m)Defined in monads-tf-0.3.0.1 · Control.Monad.Writer.Class(Monoid w, Monad m) => MonadWriter (WriterT w m)Defined in monads-tf-0.3.0.1 · Control.Monad.Writer.Class(Monoid w, Monad m) => MonadWriter (WriterT w m)Defined in monads-tf-0.3.0.1 · Control.Monad.Writer.Class(Monoid w, Monad m) => MonadWriter (RWST r w s m)Defined in monads-tf-0.3.0.1 · Control.Monad.Writer.Class(Monoid w, Monad m) => MonadWriter (RWST r w s m)Defined in monads-tf-0.3.0.1 · Control.Monad.Writer.Class