Safe Haskell	Safe
Language	Haskell2010

Data.These

Contents

Functions to get rid of These
Traversals
Case selections
Case predicates
Map operations

Description

The These type and associated operations.

Synopsis

data These a b
- = This a
- | That b
- | These a b
these :: (a -> c) -> (b -> c) -> (a -> b -> c) -> These a b -> c
fromThese :: a -> b -> These a b -> (a, b)
mergeThese :: (a -> a -> a) -> These a a -> a
mergeTheseWith :: (a -> c) -> (b -> c) -> (c -> c -> c) -> These a b -> c
here :: Applicative f => (a -> f b) -> These a t -> f (These b t)
there :: Applicative f => (a -> f b) -> These t a -> f (These t b)
justThis :: These a b -> Maybe a
justThat :: These a b -> Maybe b
justThese :: These a b -> Maybe (a, b)
catThis :: [These a b] -> [a]
catThat :: [These a b] -> [b]
catThese :: [These a b] -> [(a, b)]
partitionThese :: [These a b] -> ([(a, b)], ([a], [b]))
isThis :: These a b -> Bool
isThat :: These a b -> Bool
isThese :: These a b -> Bool
mapThese :: (a -> c) -> (b -> d) -> These a b -> These c d
mapThis :: (a -> c) -> These a b -> These c b
mapThat :: (b -> d) -> These a b -> These a d

Documentation

data These a b Source #

The These type represents values with two non-exclusive possibilities.

This can be useful to represent combinations of two values, where the combination is defined if either input is. Algebraically, the type These A B represents (A + B + AB), which doesn't factor easily into sums and products--a type like Either A (B, Maybe A) is unclear and awkward to use.

These has straightforward instances of Functor, Monad, &c., and behaves like a hybrid error/writer monad, as would be expected.

Constructors

This a
That b
These a b

Instances

Bitraversable These Source #
Instance details Defined in Data.These Methods bitraverse :: Applicative f => (a -> f c) -> (b -> f d) -> These a b -> f (These c d) #
Bifoldable These Source #
Instance details Defined in Data.These Methods bifold :: Monoid m => These m m -> m # bifoldMap :: Monoid m => (a -> m) -> (b -> m) -> These a b -> m # bifoldr :: (a -> c -> c) -> (b -> c -> c) -> c -> These a b -> c # bifoldl :: (c -> a -> c) -> (c -> b -> c) -> c -> These a b -> c #
Bifunctor These Source #
Instance details Defined in Data.These Methods bimap :: (a -> b) -> (c -> d) -> These a c -> These b d # first :: (a -> b) -> These a c -> These b c # second :: (b -> c) -> These a b -> These a c #
Semigroup a => Monad (These a) Source #
Instance details Defined in Data.These Methods (>>=) :: These a a0 -> (a0 -> These a b) -> These a b # (>>) :: These a a0 -> These a b -> These a b # return :: a0 -> These a a0 # fail :: String -> These a a0 #
Functor (These a) Source #
Instance details Defined in Data.These Methods fmap :: (a0 -> b) -> These a a0 -> These a b # (<$) :: a0 -> These a b -> These a a0 #
Semigroup a => Applicative (These a) Source #
Instance details Defined in Data.These Methods pure :: a0 -> These a a0 # (<>) :: These a (a0 -> b) -> These a a0 -> These a b # liftA2 :: (a0 -> b -> c) -> These a a0 -> These a b -> These a c # (>) :: These a a0 -> These a b -> These a b # (<*) :: These a a0 -> These a b -> These a a0 #
Foldable (These a) Source #
Instance details Defined in Data.These Methods fold :: Monoid m => These a m -> m # foldMap :: Monoid m => (a0 -> m) -> These a a0 -> m # foldr :: (a0 -> b -> b) -> b -> These a a0 -> b # foldr' :: (a0 -> b -> b) -> b -> These a a0 -> b # foldl :: (b -> a0 -> b) -> b -> These a a0 -> b # foldl' :: (b -> a0 -> b) -> b -> These a a0 -> b # foldr1 :: (a0 -> a0 -> a0) -> These a a0 -> a0 # foldl1 :: (a0 -> a0 -> a0) -> These a a0 -> a0 # toList :: These a a0 -> [a0] # null :: These a a0 -> Bool # length :: These a a0 -> Int # elem :: Eq a0 => a0 -> These a a0 -> Bool # maximum :: Ord a0 => These a a0 -> a0 # minimum :: Ord a0 => These a a0 -> a0 # sum :: Num a0 => These a a0 -> a0 # product :: Num a0 => These a a0 -> a0 #
Traversable (These a) Source #
Instance details Defined in Data.These Methods traverse :: Applicative f => (a0 -> f b) -> These a a0 -> f (These a b) # sequenceA :: Applicative f => These a (f a0) -> f (These a a0) # mapM :: Monad m => (a0 -> m b) -> These a a0 -> m (These a b) # sequence :: Monad m => These a (m a0) -> m (These a a0) #
(Eq a, Eq b) => Eq (These a b) Source #
Instance details Defined in Data.These Methods (==) :: These a b -> These a b -> Bool # (/=) :: These a b -> These a b -> Bool #
(Data a, Data b) => Data (These a b) Source #
Instance details Defined in Data.These Methods gfoldl :: (forall d b0. Data d => c (d -> b0) -> d -> c b0) -> (forall g. g -> c g) -> These a b -> c (These a b) # gunfold :: (forall b0 r. Data b0 => c (b0 -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (These a b) # toConstr :: These a b -> Constr # dataTypeOf :: These a b -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (These a b)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (These a b)) # gmapT :: (forall b0. Data b0 => b0 -> b0) -> These a b -> These a b # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> These a b -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> These a b -> r # gmapQ :: (forall d. Data d => d -> u) -> These a b -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> These a b -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> These a b -> m (These a b) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> These a b -> m (These a b) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> These a b -> m (These a b) #
(Ord a, Ord b) => Ord (These a b) Source #
Instance details Defined in Data.These Methods compare :: These a b -> These a b -> Ordering # (<) :: These a b -> These a b -> Bool # (<=) :: These a b -> These a b -> Bool # (>) :: These a b -> These a b -> Bool # (>=) :: These a b -> These a b -> Bool # max :: These a b -> These a b -> These a b # min :: These a b -> These a b -> These a b #
(Read a, Read b) => Read (These a b) Source #
Instance details Defined in Data.These Methods readsPrec :: Int -> ReadS (These a b) # readList :: ReadS [These a b] # readPrec :: ReadPrec (These a b) # readListPrec :: ReadPrec [These a b] #
(Show a, Show b) => Show (These a b) Source #
Instance details Defined in Data.These Methods showsPrec :: Int -> These a b -> ShowS # show :: These a b -> String # showList :: [These a b] -> ShowS #
Generic (These a b) Source #
Instance details Defined in Data.These Associated Types type Rep (These a b) :: * -> * # Methods from :: These a b -> Rep (These a b) x # to :: Rep (These a b) x -> These a b #
(Semigroup a, Semigroup b) => Semigroup (These a b) Source #
Instance details Defined in Data.These Methods (<>) :: These a b -> These a b -> These a b # sconcat :: NonEmpty (These a b) -> These a b # stimes :: Integral b0 => b0 -> These a b -> These a b #
(NFData a, NFData b) => NFData (These a b) Source #
Instance details Defined in Data.These Methods rnf :: These a b -> () #
type Rep (These a b) Source #
Instance details Defined in Data.These type Rep (These a b) = D1 (MetaData "These" "Data.These" "these-skinny-0.7.4-2BMqYWmhN77HfaYejJMHS0" False) (C1 (MetaCons "This" PrefixI False) (S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 a)) :+: (C1 (MetaCons "That" PrefixI False) (S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 b)) :+: C1 (MetaCons "These" PrefixI False) (S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 a) :*: S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 b))))