Safe Haskell | Safe-Inferred |
---|

- module Data.Maybe
- data MaybeErr err val
- failME :: err -> MaybeErr err val
- isSuccess :: MaybeErr err val -> Bool
- fmapM_maybe :: Monad m => (a -> m b) -> Maybe a -> m (Maybe b)
- orElse :: Maybe a -> a -> a
- mapCatMaybes :: (a -> Maybe b) -> [a] -> [b]
- allMaybes :: [Maybe a] -> Maybe [a]
- firstJust :: Maybe a -> Maybe a -> Maybe a
- firstJusts :: [Maybe a] -> Maybe a
- expectJust :: String -> Maybe a -> a
- maybeToBool :: Maybe a -> Bool
- newtype MaybeT m a = MaybeT {}

# Documentation

module Data.Maybe

fmapM_maybe :: Monad m => (a -> m b) -> Maybe a -> m (Maybe b)Source

mapCatMaybes :: (a -> Maybe b) -> [a] -> [b]Source

allMaybes :: [Maybe a] -> Maybe [a]Source

Collects a list of `Justs`

into a single `Just`

, returning `Nothing`

if
there are any `Nothings`

.

firstJusts :: [Maybe a] -> Maybe aSource

Takes a list of `Maybes`

and returns the first `Just`

if there is one, or
`Nothing`

otherwise.

expectJust :: String -> Maybe a -> aSource

maybeToBool :: Maybe a -> BoolSource