Control.Monad.Writer.Class

The MonadWriter class.

Inspired by the paper /Functional Programming with Overloading and Higher-Order Polymorphism/, Mark P Jones (http://web.cecs.pdx.edu/~mpj/pubs/springschool.html) Advanced School of Functional Programming, 1995.

Documentation

class (Monoid (WriterType m), Monad m) => MonadWriter m where

Associated Types

type WriterType m

Methods

tell :: WriterType m -> m ()

listen :: m a -> m (a, WriterType m)

pass :: m (a, WriterType m -> WriterType m) -> m a

Instances

MonadWriter m => MonadWriter (MaybeT m)

MonadWriter m => MonadWriter (IdentityT m)

(Monoid w, Monad m) => MonadWriter (WriterT w m)

(Monoid w, Monad m) => MonadWriter (WriterT w m)

MonadWriter m => MonadWriter (StateT s m)

MonadWriter m => MonadWriter (StateT s m)

MonadWriter m => MonadWriter (ReaderT r m)

(Error e, MonadWriter m) => MonadWriter (ErrorT e m)

(Monoid w, Monad m) => MonadWriter (RWST r w s m)

(Monoid w, Monad m) => MonadWriter (RWST r w s m)

listens :: MonadWriter m => (WriterType m -> b) -> m a -> m (a, b)

censor :: MonadWriter m => (WriterType m -> WriterType m) -> m a -> m a