these-0.7.3: An either-or-both data type & a generalized 'zip with padding' typeclass

Safe Haskell | None
Language | Haskell98

Data.These

Contents

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

Description

The `These` type and associated operations. Now enhanced with `Control.Lens` magic!

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)
- _This :: (Choice p, Applicative f) => p a (f a) -> p (These a b) (f (These a b))
- _That :: (Choice p, Applicative f) => p b (f b) -> p (These a b) (f (These a b))
- _These :: (Choice p, Applicative f) => p (a, b) (f (a, b)) -> p (These a b) (f (These a 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

ToJSON2 These Source # |

Methods

liftToJSON2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> These a b -> Value #

liftToJSONList2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> [These a b] -> Value #

liftToEncoding2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> These a b -> Encoding #

liftToEncodingList2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> [These a b] -> Encoding #

FromJSON2 These Source # |
Methods liftParseJSON2 :: (Value -> Parser a) -> (Value -> Parser [a]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser (These a b) # liftParseJSONList2 :: (Value -> Parser a) -> (Value -> Parser [a]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser [These a b] #
Bifunctor These Source # |
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 #
Bitraversable These Source # |
Methods bitraverse :: Applicative f => (a -> f c) -> (b -> f d) -> These a b -> f (These c d) #
Bifoldable These Source # |
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 #
Bitraversable1 These Source # |
Methods bitraverse1 :: Apply f => (a -> f b) -> (c -> f d) -> These a c -> f (These b d) # bisequence1 :: Apply f => These (f a) (f b) -> f (These a b) #
Bifoldable1 These Source # |
Methods bifold1 :: Semigroup m => These m m -> m # bifoldMap1 :: Semigroup m => (a -> m) -> (b -> m) -> These a b -> m #
Bicrosswalk These Source # |
Methods bicrosswalk :: Align f => (a -> f c) -> (b -> f d) -> These a b -> f (These c d) Source # bisequenceL :: Align f => These (f a) (f b) -> f (These a b) Source #
Semigroup c => MonadChronicle c (These c) Source # |
Methods dictate :: c -> These c () Source # disclose :: Default a => c -> These c a Source # confess :: c -> These c a Source # memento :: These c a -> These c (Either c a) Source # absolve :: a -> These c a -> These c a Source # condemn :: These c a -> These c a Source # retcon :: (c -> c) -> These c a -> These c a Source # chronicle :: These c a -> These c a Source #
Semigroup a => Monad (These a) Source # |
Methods (>>=) :: These a a -> (a -> These a b) -> These a b # (>>) :: These a a -> These a b -> These a b # return :: a -> These a a # fail :: String -> These a a #
Functor (These a) Source # |
Methods fmap :: (a -> b) -> These a a -> These a b # (<$) :: a -> These a b -> These a a #
Semigroup a => Applicative (These a) Source # |
Methods pure :: a -> These a a # (<*>) :: These a (a -> b) -> These a a -> These a b # (*>) :: These a a -> These a b -> These a b # (<*) :: These a a -> These a b -> These a a #
Foldable (These a) Source # |

Methods

fold :: Monoid m => These a m -> m #

foldMap :: Monoid m => (a -> m) -> These a a -> m #

foldr :: (a -> b -> b) -> b -> These a a -> b #

foldr' :: (a -> b -> b) -> b -> These a a -> b #

foldl :: (b -> a -> b) -> b -> These a a -> b #

foldl' :: (b -> a -> b) -> b -> These a a -> b #

foldr1 :: (a -> a -> a) -> These a a -> a #

foldl1 :: (a -> a -> a) -> These a a -> a #

toList :: These a a -> [a] #

null :: These a a -> Bool #

length :: These a a -> Int #

elem :: Eq a => a -> These a a -> Bool #

maximum :: Ord a => These a a -> a #

minimum :: Ord a => These a a -> a #

sum :: Num a => These a a -> a #

product :: Num a => These a a -> a #

Traversable (These a) Source # |
Methods traverse :: Applicative f => (a -> f b) -> These a a -> f (These a b) # sequenceA :: Applicative f => These a (f a) -> f (These a a) # mapM :: Monad m => (a -> m b) -> These a a -> m (These a b) # sequence :: Monad m => These a (m a) -> m (These a a) #
ToJSON a => ToJSON1 (These a) Source # |
Methods liftToJSON :: (a -> Value) -> ([a] -> Value) -> These a a -> Value # liftToJSONList :: (a -> Value) -> ([a] -> Value) -> [These a a] -> Value # liftToEncoding :: (a -> Encoding) -> ([a] -> Encoding) -> These a a -> Encoding # liftToEncodingList :: (a -> Encoding) -> ([a] -> Encoding) -> [These a a] -> Encoding #
FromJSON a => FromJSON1 (These a) Source # |
Methods liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (These a a) # liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [These a a] #
Semigroup a => Apply (These a) Source # |
Methods (<.>) :: These a (a -> b) -> These a a -> These a b # (.>) :: These a a -> These a b -> These a b # (<.) :: These a a -> These a b -> These a a #
Semigroup a => Bind (These a) Source # |
Methods (>>-) :: These a a -> (a -> These a b) -> These a b # join :: These a (These a a) -> These a a #
Crosswalk (These a) Source # |
Methods crosswalk :: Align f => (a -> f b) -> These a a -> f (These a b) Source # sequenceL :: Align f => These a (f a) -> f (These a a) Source #
(Eq b, Eq a) => Eq (These a b) Source # |
Methods (==) :: These a b -> These a b -> Bool # (/=) :: These a b -> These a b -> Bool #
(Data b, Data a) => Data (These a b) Source # |

Methods

gfoldl :: (forall d c. Data d => c (d -> c) -> d -> c c) -> (forall g. g -> c g) -> These a b -> c (These a b) #

gunfold :: (forall c r. Data c => c (c -> 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 c. Data c => c -> c) -> 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 b, Ord a) => Ord (These a b) Source # |
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 b, Read a) => Read (These a b) Source # |
Methods readsPrec :: Int -> ReadS (These a b) # readList :: ReadS [These a b] # readPrec :: ReadPrec (These a b) # readListPrec :: ReadPrec [These a b] #
(Show b, Show a) => Show (These a b) Source # |
Methods showsPrec :: Int -> These a b -> ShowS # show :: These a b -> String # showList :: [These a b] -> ShowS #
Generic (These a b) Source # |
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 # |
Methods (<>) :: These a b -> These a b -> These a b # sconcat :: NonEmpty (These a b) -> These a b # stimes :: Integral b => b -> These a b -> These a b #
(Function a, Function b) => Function (These a b) Source # |
Methods function :: (These a b -> b) -> These a b :-> b #
(Arbitrary a, Arbitrary b) => Arbitrary (These a b) Source # |
Methods arbitrary :: Gen (These a b) # shrink :: These a b -> [These a b] #
(CoArbitrary a, CoArbitrary b) => CoArbitrary (These a b) Source # |
Methods coarbitrary :: These a b -> Gen b -> Gen b #
(Hashable a, Hashable b) => Hashable (These a b) Source # |
Methods hashWithSalt :: Int -> These a b -> Int # hash :: These a b -> Int #
(ToJSON a, ToJSON b) => ToJSON (These a b) Source # |
Methods toJSON :: These a b -> Value # toEncoding :: These a b -> Encoding # toJSONList :: [These a b] -> Value # toEncodingList :: [These a b] -> Encoding #
(FromJSON a, FromJSON b) => FromJSON (These a b) Source # |
Methods parseJSON :: Value -> Parser (These a b) # parseJSONList :: Value -> Parser [These a b] #
(Binary a, Binary b) => Binary (These a b) Source # |
Methods put :: These a b -> Put # get :: Get (These a b) # putList :: [These a b] -> Put #
(NFData a, NFData b) => NFData (These a b) Source # |
Methods rnf :: These a b -> () #
type Rep (These a b) Source # |

type Rep (These a b) = D1 (MetaData "These" "Data.These" "these-0.7.3-6Gs0TxQLIRJ4gQf6KstsdP" False) ((:+:) (C1 (MetaCons "This" PrefixI False) (S1 (MetaSel (Nothing Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 a))) ((:+:) (C1 (MetaCons "That" PrefixI False) (S1 (MetaSel (Nothing Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 b))) (C1 (MetaCons "These" PrefixI False) ((:*:) (S1 (MetaSel (Nothing Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 a)) (S1 (MetaSel (Nothing Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 b))))))

# Functions to get rid of `These`

these :: (a -> c) -> (b -> c) -> (a -> b -> c) -> These a b -> c Source #

Case analysis for the `These` type.

fromThese :: a -> b -> These a b -> (a, b) Source #

Takes two default values and produces a tuple.

mergeThese :: (a -> a -> a) -> These a a -> a Source #

Coalesce with the provided operation.

mergeTheseWith :: (a -> c) -> (b -> c) -> (c -> c -> c) -> These a b -> c Source #

BiMap and coalesce results with the provided operation.

# Traversals

here :: Applicative f => (a -> f b) -> These a t -> f (These b t) Source #

A `Traversal` of the first half of a `These`, suitable for use with `Control.Lens`.

there :: Applicative f => (a -> f b) -> These t a -> f (These t b) Source #

A `Traversal` of the second half of a `These`, suitable for use with `Control.Lens`.

# Prisms

_This :: (Choice p, Applicative f) => p a (f a) -> p (These a b) (f (These a b)) Source #

A `Prism` selecting the `This` constructor.

_That :: (Choice p, Applicative f) => p b (f b) -> p (These a b) (f (These a b)) Source #

A `Prism` selecting the `That` constructor.

_These :: (Choice p, Applicative f) => p (a, b) (f (a, b)) -> p (These a b) (f (These a b)) Source #

A `Prism` selecting the `These` constructor. `These` names are ridiculous!

# Case selections

justThis :: These a b -> Maybe a Source #

    justThis = preview _This

justThat :: These a b -> Maybe b Source #

    justThat = preview _That

justThese :: These a b -> Maybe (a, b) Source #

    justThese = preview _These

catThis :: [These a b] -> [a] Source #

Select all `This` constructors from a list.

catThat :: [These a b] -> [b] Source #

Select all `That` constructors from a list.

catThese :: [These a b] -> [(a, b)] Source #

Select all `These` constructors from a list.

partitionThese :: [These a b] -> ([(a, b)], ([a], [b])) Source #

Select each constructor and partition them into separate lists.

# Case predicates

isThis :: These a b -> Bool Source #

    isThis = isJust . justThis

isThat :: These a b -> Bool Source #

    isThat = isJust . justThat

isThese :: These a b -> Bool Source #

    isThese = isJust . justThese

# Map operations

mapThese :: (a -> c) -> (b -> d) -> These a b -> These c d Source #

`Bifunctor` map.

mapThis :: (a -> c) -> These a b -> These c b Source #

    mapThis = over here

mapThat :: (b -> d) -> These a b -> These a d Source #

    mapThat = over there

For zipping and unzipping of structures with `These` values, see Data.Align.