Safe Haskell | Safe-Inferred |
---|---|
Language | Haskell2010 |
Synopsis
- newtype MaybeT (m :: Type -> Type) a = MaybeT {}
- maybeToExceptT :: forall (m :: Type -> Type) e a. Functor m => e -> MaybeT m a -> ExceptT e m a
- mapMaybeT :: (m (Maybe a) -> n (Maybe b)) -> MaybeT m a -> MaybeT n b
- exceptToMaybeT :: forall (m :: Type -> Type) e a. Functor m => ExceptT e m a -> MaybeT m a
Documentation
newtype MaybeT (m :: Type -> Type) a #
The parameterizable maybe monad, obtained by composing an arbitrary
monad with the Maybe
monad.
Computations are actions that may produce a value or exit.
The return
function yields a computation that produces that
value, while >>=
sequences two subcomputations, exiting if either
computation does.
Instances
Orphan instances
MonadTransCoerce MaybeT Source # | |
MonadTransHoist MaybeT Source # | |
MonadTransTunnel MaybeT Source # | |
TransConstraint MonadFail MaybeT Source # | |
TransConstraint MonadFix MaybeT Source # | |
TransConstraint MonadIO MaybeT Source # | |
TransConstraint Functor MaybeT Source # | |
TransConstraint Monad MaybeT Source # | |
TransConstraint MonadPlus MaybeT Source # | |
TransConstraint MonadInner MaybeT Source # | |
hasTransConstraint :: forall (m :: Type -> Type). MonadInner m => Dict (MonadInner (MaybeT m)) Source # | |
MonadException m => MonadException (MaybeT m) Source # | |
MonadInner m => MonadInner (MaybeT m) Source # | |
MonadCatch e m => MonadCatch (Maybe e) (MaybeT m) Source # | |
MonadThrow e m => MonadThrow (Maybe e) (MaybeT m) Source # | |