Copyright	Vadim Vinnik 2017
License	BSD3
Maintainer	[email protected]
Stability	experimental
Portability	portable
Safe Haskell	Safe
Language	Haskell98

Data.Empty

Description

An always empty data structure, i.e. a degenerate container that contains no elements but is aware of the (missing) elements' type, and is a first-class citizen of a number of type classes. E.g. fmapping of any function over Empty is also Empty, two Empty container can be mappended that gives Empty again etc.

Synopsis

Documentation

data Empty a Source #

the empty container

Constructors

Empty

Instances

Monad Empty Source #
Methods (>>=) :: Empty a -> (a -> Empty b) -> Empty b # (>>) :: Empty a -> Empty b -> Empty b # return :: a -> Empty a # fail :: String -> Empty a #
Functor Empty Source #
Methods fmap :: (a -> b) -> Empty a -> Empty b # (<$) :: a -> Empty b -> Empty a #
Applicative Empty Source #
Methods pure :: a -> Empty a # (<>) :: Empty (a -> b) -> Empty a -> Empty b # (>) :: Empty a -> Empty b -> Empty b # (<*) :: Empty a -> Empty b -> Empty a #
Foldable Empty Source #
Methods fold :: Monoid m => Empty m -> m # foldMap :: Monoid m => (a -> m) -> Empty a -> m # foldr :: (a -> b -> b) -> b -> Empty a -> b # foldr' :: (a -> b -> b) -> b -> Empty a -> b # foldl :: (b -> a -> b) -> b -> Empty a -> b # foldl' :: (b -> a -> b) -> b -> Empty a -> b # foldr1 :: (a -> a -> a) -> Empty a -> a # foldl1 :: (a -> a -> a) -> Empty a -> a # toList :: Empty a -> [a] # null :: Empty a -> Bool # length :: Empty a -> Int # elem :: Eq a => a -> Empty a -> Bool # maximum :: Ord a => Empty a -> a # minimum :: Ord a => Empty a -> a # sum :: Num a => Empty a -> a # product :: Num a => Empty a -> a #
Traversable Empty Source #
Methods traverse :: Applicative f => (a -> f b) -> Empty a -> f (Empty b) # sequenceA :: Applicative f => Empty (f a) -> f (Empty a) # mapM :: Monad m => (a -> m b) -> Empty a -> m (Empty b) # sequence :: Monad m => Empty (m a) -> m (Empty a) #
Alternative Empty Source #
Methods empty :: Empty a # (<\|>) :: Empty a -> Empty a -> Empty a # some :: Empty a -> Empty [a] # many :: Empty a -> Empty [a] #
MonadPlus Empty Source #
Methods mzero :: Empty a # mplus :: Empty a -> Empty a -> Empty a #
Eq (Empty a) Source #
Methods (==) :: Empty a -> Empty a -> Bool # (/=) :: Empty a -> Empty a -> Bool #
Ord (Empty a) Source #
Methods compare :: Empty a -> Empty a -> Ordering # (<) :: Empty a -> Empty a -> Bool # (<=) :: Empty a -> Empty a -> Bool # (>) :: Empty a -> Empty a -> Bool # (>=) :: Empty a -> Empty a -> Bool # max :: Empty a -> Empty a -> Empty a # min :: Empty a -> Empty a -> Empty a #
Monoid (Empty a) Source #
Methods mempty :: Empty a # mappend :: Empty a -> Empty a -> Empty a # mconcat :: [Empty a] -> Empty a #

unwrap :: Empty a -> a Source #

obtain the (missing) value from the container -- always fails