Hoogle Search

Within LTS Haskell 24.6 (ghc-9.10.2)

Note that Stackage only displays results for the latest LTS and Nightly snapshot. Learn more.

Exact lookup

1. maybeOption :: a -> Bool -> (a -> a) -> Maybe a -> Maybe a

   configuration-tools	Configuration.Utils.Maybe

   Command line parser for record Maybe values

   Example:

   data Setting = Setting
   { _setA ∷ !Int
   , _setB ∷ !String
   }
   deriving (Show, Read, Eq, Ord, Typeable)
   
   $(makeLenses ''Setting)
   
   defaultSetting ∷ Setting
   defaultSetting = Setting
   { _setA = 0
   , _setB = 1
   }
   
   instance ToJSON Setting where
   toJSON setting = object
   [ "a" .= _setA setting
   , "b" .= _setB setting
   ]
   
   instance FromJSON (Setting → Setting) where
   parseJSON = withObject "Setting" $ \o → id
   <$< setA ..: "a" % o
   <*< setB ..: "b" % o
   
   instance FromJSON Setting where
   parseJSON v = parseJSON v <*> pure defaultSetting
   
   pSetting ∷ MParser Setting
   pSetting = id
   <$< setA .:: option auto
   % short 'a'
   <> metavar "INT"
   <> help "set a"
   <*< setB .:: option auto
   % short 'b'
   <> metavar "INT"
   <> help "set b"
   
   -- | Use 'Setting' as 'Maybe' in a configuration:
   --
   data Config = Config
   { _maybeSetting ∷ !(Maybe Setting)
   }
   deriving (Show, Read, Eq, Ord, Typeable)
   
   $(makeLenses ''Config)
   
   defaultConfig ∷ Config
   defaultConfig = Config
   { _maybeSetting = defaultSetting
   }
   
   instance ToJSON Config where
   toJSON config = object
   [ "setting" .= maybeSetting
   ]
   
   instance FromJSON (Config → Config) where
   parseJSON = withObject "Config" $ \o → id
   <$< maybeSetting %.: "setting" % o
   
   pConfig ∷ MParser Config
   pConfig = id
   <$< maybeSetting %:: (maybeOption defaultSetting
   <$> pEnableSetting
   <*> pSetting)
   where
   pEnableSetting = boolOption
   % long "setting-enable"
   <> value False
   <> help "Enable configuration flags for setting"
   

2. maybeHolds :: Property p v => p -> v -> Maybe v

   data-checked	Data.Checked

   Return Just v if p holds and Nothing overwise.

3. maybeHolds :: Property p v => p -> v -> Maybe v

   data-checked	Data.Checked.Strict

   Return Just v if p holds and Nothing overwise.

4. maybeM :: Monad m => m b -> (a -> m b) -> m (Maybe a) -> m b

   distribution-opensuse	OpenSuse.Prelude

   Monadic generalisation of maybe.

5. maybeToExceptS :: forall (m :: Type -> Type) a b . (Functor m, Monad m) => MSF (MaybeT m) a b -> MSF (ExceptT () m) a b

   dunai	Control.Monad.Trans.MSF.Except

   Converts an MSF in MaybeT to an MSF in ExceptT. Whenever Nothing is thrown, throw () instead.

6. maybeExit :: forall (m :: Type -> Type) a . Monad m => MSF (MaybeT m) (Maybe a) a

   dunai	Control.Monad.Trans.MSF.Maybe

   Just a is passed along, Nothing causes the whole MSF to exit.

7. maybeToExceptS :: forall (m :: Type -> Type) a b . (Functor m, Monad m) => MSF (MaybeT m) a b -> MSF (ExceptT () m) a b

   dunai	Control.Monad.Trans.MSF.Maybe

   Converts an MSF in MaybeT to an MSF in ExceptT. Whenever Nothing is thrown, throw () instead.

8. maybeToExceptT :: forall (m :: Type -> Type) e a . Functor m => e -> MaybeT m a -> ExceptT e m a

   dunai	Control.Monad.Trans.MSF.Maybe

   Convert a MaybeT computation to ExceptT, with a default exception value.

9. maybeModTime :: FilePath -> IO (Maybe UTCTime)

   dyre	Config.Dyre.Paths

   Check if a file exists. If it exists, return Just the modification time. If it doesn't exist, return Nothing.

10. maybeEither :: Maybe a -> Either () a

    errors-ext	Control.Error.Extensions

    Converts Maybe to Either. Specialization of maybe.

    maybeEither . eitherMaybe = id
    

Page 50 of many | Previous | Next