Control.Monad.Writer.Class

Control.Monad.Writer.Class

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

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

Methods

tell :: w -> m ()

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

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

show/hide

Instances

Monoid w => MonadWriter w (Writer w)

Monoid w => MonadWriter w (Writer w)

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

MonadWriter w m => MonadWriter w (ReaderT r m)

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)

(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)

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

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