Safe Haskell | Safe-Inferred |
---|
Extend Maybe
by common operations for the Maybe
type.
Note: since this module is usually imported unqualified,
we do not use short names, but all names contain Maybe
,
Just
, or 'Nothing.
- unionMaybeWith :: (a -> a -> a) -> Maybe a -> Maybe a -> Maybe a
- unzipMaybe :: Maybe (a, b) -> (Maybe a, Maybe b)
- filterMaybe :: (a -> Bool) -> a -> Maybe a
- forMaybe :: [a] -> (a -> Maybe b) -> [b]
- caseMaybe :: Maybe a -> b -> (a -> b) -> b
- maybeM :: Monad m => m b -> (a -> m b) -> m (Maybe a) -> m b
- fromMaybeM :: Monad m => m a -> m (Maybe a) -> m a
- caseMaybeM :: Monad m => m (Maybe a) -> m b -> (a -> m b) -> m b
- ifJustM :: Monad m => m (Maybe a) -> (a -> m b) -> m b -> m b
- whenJust :: Monad m => Maybe a -> (a -> m ()) -> m ()
- whenJustM :: Monad m => m (Maybe a) -> (a -> m ()) -> m ()
Collection operations.
unionMaybeWith :: (a -> a -> a) -> Maybe a -> Maybe a -> Maybe aSource
unionWith
for collections of size <= 1.
unzipMaybe :: Maybe (a, b) -> (Maybe a, Maybe b)Source
Unzipping a list of length <= 1.
filterMaybe :: (a -> Bool) -> a -> Maybe aSource
Filtering a singleton list.
filterMaybe p a =listToMaybe
(filter
p [a])
Conditionals and loops.
caseMaybe :: Maybe a -> b -> (a -> b) -> bSource
Version of maybe
with different argument ordering.
Often, we want to case on a Maybe
, do something interesting
in the Just
case, but only a default action in the Nothing
case. Then, the argument ordering of caseMaybe
is preferable.
caseMaybe m err f = flip (maybe err) m f
Monads and Maybe.
fromMaybeM :: Monad m => m a -> m (Maybe a) -> m aSource
Monadic version of fromMaybe
.
caseMaybeM :: Monad m => m (Maybe a) -> m b -> (a -> m b) -> m bSource
ifJustM :: Monad m => m (Maybe a) -> (a -> m b) -> m b -> m bSource
caseMaybeM
with flipped branches.
whenJustM :: Monad m => m (Maybe a) -> (a -> m ()) -> m ()Source
caseMaybeM
without the Nothing
case.