Copyright	(c) Andy Gill 2001, (c) Oregon Graduate Institute of Science and Technology, 2001
License	BSD-style (see the file libraries/base/LICENSE)
Maintainer	libraries@haskell.org
Stability	experimental
Portability	non-portable (multi-param classes, functional dependencies)
Safe Haskell	Safe-Inferred
Language	Haskell98

Control.Monad.Writer.Class

Description

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 w, Monad m) => MonadWriter w m | m -> w where Source

Methods

tell :: w -> m () Source

listen :: m a -> m (a, w) Source

pass :: m (a, w -> w) -> m a Source

Instances

Monoid w => MonadWriter w (Writer w)
MonadWriter w m => MonadWriter w (IdentityT m)
Monoid w => MonadWriter w (Writer w)
MonadWriter w m => MonadWriter w (StateT s m)
MonadWriter w m => MonadWriter w (StateT s m)
(Monoid w, Monad m) => MonadWriter w (WriterT w m)
MonadWriter w m => MonadWriter w (ReaderT r m)
(Error e, MonadWriter w m) => MonadWriter w (ErrorT e m)
(Monoid w, Monad m) => MonadWriter w (WriterT w m)
Monoid w => MonadWriter w (RWS r w s)
Monoid w => MonadWriter w (RWS r w s)
(Monoid w, Monad m) => MonadWriter w (RWST r w s m)
(Monoid w, Monad m) => MonadWriter w (RWST r w s m)

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

censor :: MonadWriter w m => (w -> w) -> m a -> m a Source