these-0.7.6: An either-or-both data type & a generalized 'zip with padding' typeclass

Safe Haskell | None
Language | Haskell2010

Data.These

Contents

- Functions to get rid of `These`
- Traversals
- Half selections
- Prisms
- Case selections
- Case predicates
- Map operations
- Associativity and commutativity

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)
- justHere :: These a b -> Maybe a
- justThere :: These a b -> Maybe b
- _This :: Prism' (These a b) a
- _That :: Prism' (These a b) b
- _These :: Prism' (These a b) (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
- bitraverseThese :: Applicative f => (a -> f c) -> (b -> f d) -> These a b -> f (These c d)
- swap :: These a b -> These b a
- assoc :: These a (These b c) -> These (These a b) c
- reassoc :: These (These a b) c -> These a (These b c)

# 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.

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

Constructors

This a |
That b |
These a b |

Instances

ToJSON2 These Source # | Since: 0.7.2

Instance details

Defined in Data.These

Methods

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

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

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

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

FromJSON2 These Source # | Since: 0.7.2
Instance details Defined in Data.These Methods liftParseJSON2 :: (Value -> Parser a) -> (Value -> Parser [a]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser (These a b) Source # liftParseJSONList2 :: (Value -> Parser a) -> (Value -> Parser [a]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser [These a b] Source #
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)
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 #
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
Bitraversable1 These Source # |
Instance details Defined in Data.These Methods bitraverse1 :: Apply f => (a -> f b) -> (c -> f d) -> These a c -> f (These b d) Source # bisequence1 :: Apply f => These (f a) (f b) -> f (These a b) Source #
Swapped These Source # | Since: 0.7.6
Instance details Defined in Data.These Methods swapped :: Iso (These a b) (These c d) (These b a) (These d c) Source #
Bifoldable1 These Source # |
Instance details Defined in Data.These Methods bifold1 :: Semigroup m => These m m -> m Source # bifoldMap1 :: Semigroup m => (a -> m) -> (b -> m) -> These a b -> m Source #
Arbitrary2 These Source # | Since: 0.7.4
Instance details Defined in Data.These Methods liftArbitrary2 :: Gen a -> Gen b -> Gen (These a b) liftShrink2 :: (a -> [a]) -> (b -> [b]) -> These a b -> [These a b]
Bicrosswalk These Source # |
Instance details Defined in Data.Align 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 # |

Instance details

Defined in Control.Monad.Chronicle.Class

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 # |
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)
ToJSON a => ToJSON1 (These a) Source # | Since: 0.7.2
Instance details Defined in Data.These Methods liftToJSON :: (a0 -> Value) -> ([a0] -> Value) -> These a a0 -> Value Source # liftToJSONList :: (a0 -> Value) -> ([a0] -> Value) -> [These a a0] -> Value Source # liftToEncoding :: (a0 -> Encoding) -> ([a0] -> Encoding) -> These a a0 -> Encoding Source # liftToEncodingList :: (a0 -> Encoding) -> ([a0] -> Encoding) -> [These a a0] -> Encoding Source #
FromJSON a => FromJSON1 (These a) Source # | Since: 0.7.2
Instance details Defined in Data.These Methods liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (These a a0) Source # liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [These a a0] Source #
Semigroup a => Apply (These a) Source # |
Instance details Defined in Data.These Methods (<.>) :: These a (a0 -> b) -> These a a0 -> These a b Source # (.>) :: These a a0 -> These a b -> These a b Source # (<.) :: These a a0 -> These a b -> These a a0 Source # liftF2 :: (a0 -> b -> c) -> These a a0 -> These a b -> These a c Source #
Semigroup a => Bind (These a) Source # |
Instance details Defined in Data.These Methods (>>-) :: These a a0 -> (a0 -> These a b) -> These a b Source # join :: These a (These a a0) -> These a a0 Source #
Arbitrary a => Arbitrary1 (These a) Source # | Since: 0.7.4
Instance details Defined in Data.These Methods liftArbitrary :: Gen a0 -> Gen (These a a0) liftShrink :: (a0 -> [a0]) -> These a a0 -> [These a a0]
Crosswalk (These a) Source # |
Instance details Defined in Data.Align Methods crosswalk :: Align f => (a0 -> f b) -> These a a0 -> f (These a b) Source # sequenceL :: Align f => These a (f a0) -> f (These a a0) Source #
(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) :: Type -> Type 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 #
(Hashable a, Hashable b) => Hashable (These a b) Source # |
Instance details Defined in Data.These Methods hashWithSalt :: Int -> These a b -> Int Source # hash :: These a b -> Int Source #
(ToJSON a, ToJSON b) => ToJSON (These a b) Source # | Since: 0.7.1
Instance details Defined in Data.These Methods toJSON :: These a b -> Value Source # toEncoding :: These a b -> Encoding Source # toJSONList :: [These a b] -> Value Source # toEncodingList :: [These a b] -> Encoding Source #
(FromJSON a, FromJSON b) => FromJSON (These a b) Source # | Since: 0.7.1
Instance details Defined in Data.These Methods parseJSON :: Value -> Parser (These a b) Source # parseJSONList :: Value -> Parser [These a b] Source #
(Arbitrary a, Arbitrary b) => Arbitrary (These a b) Source # | Since: 0.7.1
Instance details Defined in Data.These Methods arbitrary :: Gen (These a b) shrink :: These a b -> [These a b]
(CoArbitrary a, CoArbitrary b) => CoArbitrary (These a b) Source # | Since: 0.7.1
Instance details Defined in Data.These Methods coarbitrary :: These a b -> Gen b0 -> Gen b0
(Function a, Function b) => Function (These a b) Source # | Since: 0.7.1
Instance details Defined in Data.These Methods function :: (These a b -> b0) -> These a b :-> b0
(NFData a, NFData b) => NFData (These a b) Source # | Since: 0.7.1
Instance details Defined in Data.These Methods rnf :: These a b -> ()
(Binary a, Binary b) => Binary (These a b) Source # | Since: 0.7.1
Instance details Defined in Data.These Methods put :: These a b -> Put get :: Get (These a b) putList :: [These a b] -> Put
type Rep (These a b) Source # |

Instance details

Defined in Data.These

type Rep (These a b) = D1 (MetaData "These" "Data.These" "these-0.7.6-5N0J0hCdRq395stDsA3zLH" 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))))

# 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.

    here :: Traversal (These a t) (These b t) a b

    >>> over here show (That 1)
    That 1

    >>> over here show (These 'a' 2)
    These "'a'" 2

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.

    there :: Traversal (These t b) (These t b) a b

    >>> over there show (That 1)
    That "1"

    >>> over there show (These 'a' 2)
    These 'a' "2"

# Half selections

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

    justHere = preview here

    >>> justHere (This 'x')
    Just 'x'

    >>> justHere (That 'y')
    Nothing

    >>> justHere (These 'x' 'y')
    Just 'x'

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

    justThere = preview there

    >>> justThere (This 'x')
    Nothing

    >>> justThere (That 'y')
    Just 'y'

    >>> justThere (These 'x' 'y')
    Just 'y'

# Prisms

_This :: Prism' (These a b) a Source #

A `Prism'` selecting the `This` constructor.

Note: cannot change type.

_That :: Prism' (These a b) b Source #

A `Prism'` selecting the `That` constructor.

Note: cannot change type.

_These :: Prism' (These a b) (a, b) Source #

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

Note: cannot change type.

# 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

bitraverseThese :: Applicative f => (a -> f c) -> (b -> f d) -> These a b -> f (These c d) Source #

`Bitraversable`.

Since: 0.7.5

# Associativity and commutativity

swap :: These a b -> These b a Source #

`These` is commutative.

    swap . swap = id

Since: 0.7.6

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

`These` is associative.

    assoc . reassoc = id
    reassoc . assoc = id

Since: 0.7.6

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

'These is associative. See `assoc`.

Since: 0.7.6