Safe Haskell | Safe |
---|---|
Language | Haskell2010 |
Provides reexports of MonadWriter
and related helpers.
Since: rio-0.1.4.0
Documentation
class (Monoid w, Monad m) => MonadWriter w (m :: * -> *) | m -> w where #
embeds a simple writer action.writer
(a,w)
is an action that produces the output tell
ww
.
is an action that executes the action listen
mm
and adds
its output to the value of the computation.
pass :: m (a, w -> w) -> m a #
is an action that executes the action pass
mm
, which
returns a value and a function, and returns the value, applying
the function to the output.
Instances
(Monoid w, HasWriteRef w env) => MonadWriter w (RIO env) # | |
MonadWriter w m => MonadWriter w (MaybeT m) | |
Monoid w => MonadWriter w ((,) w) | NOTE: This instance is only defined for Since: mtl-2.2.2 |
(Monoid w, Monad m) => MonadWriter w (WriterT w m) | |
(Monoid w, Monad m) => MonadWriter w (WriterT w m) | |
MonadWriter w m => MonadWriter w (StateT s m) | |
MonadWriter w m => MonadWriter w (StateT s m) | |
MonadWriter w m => MonadWriter w (IdentityT m) | |
MonadWriter w m => MonadWriter w (ExceptT e m) | Since: mtl-2.2 |
(Error e, MonadWriter w m) => MonadWriter w (ErrorT e m) | |
MonadWriter w m => MonadWriter w (ReaderT r m) | |
(Monoid w, Monad m) => MonadWriter w (RWST r w s m) | |
(Monoid w, Monad m) => MonadWriter w (RWST r w s m) | |