Portability	non-portable (multi-param classes, functional dependencies)
Stability	experimental
Maintainer	libraries@haskell.org

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 whereSource

Methods

tell :: w -> m ()Source

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

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

Instances

(Monoid w, Monad m, MonadTrans t, Monad (t (WriterT w m)), Monad (t (StateT w m))) => MonadWriter w (t (WriterT w m))
(Monoid w, MonadTrans t, Monad (t (Writer w)), Monad (t (State w))) => MonadWriter w (t (Writer w))
Monoid w => MonadWriter w (Writer w)
(Monoid w, Monad m, MonadTrans t, Monad (t (WriterT w m)), Monad (t (StateT w m))) => MonadWriter w (t (WriterT w m))
(Monoid w, MonadTrans t, Monad (t (Writer w)), Monad (t (State w))) => MonadWriter w (t (Writer w))
Monoid w => MonadWriter w (Writer w)
(Monoid w, Monad m) => MonadWriter w (WriterT w m)
(Monoid w, Monad m) => MonadWriter w (WriterT w m)

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

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