Control.Monad.Nope.Class

attempt :: forall m a. MonadNope m => m a -> m (Maybe a)

Return Just if the given action succeeds, Nothing if it nopes.

class MonadNope :: (Type -> Type) -> Constraintclass (MonadNuhUh m) <= MonadNope m  where

The MonadNope type class represents those monads which support catching nopes.

• yup x h calls the nope handler h if a nope is thrown during the evaluation of x.

An implementation is provided for MaybeT, and for other monad transformers defined in this library.

Laws:

• Catch: yup nope h = h
• Pure: yup (pure a) h = pure a

Members

• yup :: forall a. m a -> m a -> m a

Instances

• (Monad m) => MonadNope (MaybeT m)
• (MonadNope m) => MonadNope (ExceptT e m)
• (MonadNope m) => MonadNope (IdentityT m)
• (MonadNope m) => MonadNope (ReaderT r m)
• (MonadNope m) => MonadNope (StateT s m)
• (Monoid w, MonadNope m) => MonadNope (WriterT w m)
• MonadNope Maybe

class MonadNuhUh :: (Type -> Type) -> Constraintclass (Monad m) <= MonadNuhUh m  where

The MonadNuhUh type class represents those monads which support Nothing via nope, where nope halts.

An implementation is provided for MaybeT, (TODO) and for other monad transformers defined in this library.

Laws:

• Left zero: nope >>= h = nope

Members

• nope :: forall a. m a

Instances

• (Monad m) => MonadNuhUh (MaybeT m)
• (MonadNuhUh m) => MonadNuhUh (ExceptT e m)
• (MonadNuhUh m) => MonadNuhUh (IdentityT m)
• (MonadNuhUh m) => MonadNuhUh (ReaderT r m)
• (MonadNuhUh m) => MonadNuhUh (StateT s m)
• (Monoid w, MonadNuhUh m) => MonadNuhUh (WriterT w m)
• MonadNuhUh Maybe

liftMaybe :: forall m a. MonadNuhUh m => Maybe a -> m a

Lift a Maybe value to a MonadNuhUh monad.

withResource :: forall m r a. MonadNope m => m r -> (r -> m Unit) -> (r -> m a) -> m a

Make sure that a resource is cleaned up in the event of a nope. The release action is called regardless of whether the body action nopes or returns.