Control.Monad.Writer.Interface

Definitions

interface MonadWriter : Type -> (Type -> Type) -> Type

  MonadWriter interface
  
  tell is like tell on the MUD's it shouts to monad
  what you want to be heard. The monad carries this 'packet'
  upwards, merging it if needed (hence the Monoid requirement).
  
  listen listens to a monad acting, and returns what the monad "said".
  
  pass lets you provide a writer transformer which changes internals of
  the written object.

Parameters: w, m
Constraints: Monoid w, Monad m
Methods:

writer : (a, w) -> m a

  `writer (a,w)` embeds a simple writer action.

tell : w -> m ()

  `tell w` is an action that produces the output `w`.

listen : m a -> m (a, w)

  `listen m` is an action that executes the action `m` and adds
  its output to the value of the computation.

pass : m (a, w -> w) -> m a

  `pass m` is an action that executes the action `m`, which
  returns a value and a function, and returns the value, applying
  the function to the output.

Implementations:

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

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

MonadWriter w m => MonadWriter w (EitherT e m)

MonadWriter w m => MonadWriter w (MaybeT m)

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

MonadWriter w m => MonadWriter w (StateT s m)

writer : MonadWriter w m => (a, w) -> m a

  `writer (a,w)` embeds a simple writer action.

Totality: total
Visibility: public export

tell : MonadWriter w m => w -> m ()

  `tell w` is an action that produces the output `w`.

Totality: total
Visibility: public export

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

  `listen m` is an action that executes the action `m` and adds
  its output to the value of the computation.

Totality: total
Visibility: public export

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

  `pass m` is an action that executes the action `m`, which
  returns a value and a function, and returns the value, applying
  the function to the output.

Totality: total
Visibility: public export

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

  `listens f m` is an action that executes the action `m` and adds
  the result of applying @f@ to the output to the value of the computation.

Totality: total
Visibility: public export

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

  `censor f m` is an action that executes the action `m` and
  applies the function `f` to its output, leaving the return value
  unchanged.

Totality: total
Visibility: public export