Modulethese-skinny-0.7.6Haskell2010

Data.These

The These type and associated operations.

1 type
19 values

Packagethese-skinny-0.7.6
Exports20
LanguageHaskell2010
LicenceBSD-3-Clause
SourceThese.hs

datadata These a b

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

Instances17Bifoldable, Bifunctor, Bitraversable, Monad, Functor, Applicative, …

Bifoldable TheseDefined in these-skinny-0.7.6 · Data.These
Bifunctor TheseDefined in these-skinny-0.7.6 · Data.These
Bitraversable TheseDefined in these-skinny-0.7.6 · Data.These
Semigroup a => Monad (These a)Defined in these-skinny-0.7.6 · Data.These
Functor (These a)Defined in these-skinny-0.7.6 · Data.These
Semigroup a => Applicative (These a)Defined in these-skinny-0.7.6 · Data.These
Foldable (These a)Defined in these-skinny-0.7.6 · Data.These
Traversable (These a)Defined in these-skinny-0.7.6 · Data.These
(Eq a, Eq b) => Eq (These a b)Defined in these-skinny-0.7.6 · Data.These
(Data a, Data b) => Data (These a b)Defined in these-skinny-0.7.6 · Data.These
(Ord a, Ord b) => Ord (These a b)Defined in these-skinny-0.7.6 · Data.These
(Read a, Read b) => Read (These a b)Defined in these-skinny-0.7.6 · Data.These
(Show a, Show b) => Show (These a b)Defined in these-skinny-0.7.6 · Data.These
Generic (These a b)Defined in these-skinny-0.7.6 · Data.These
(Semigroup a, Semigroup b) => Semigroup (These a b)Defined in these-skinny-0.7.6 · Data.These
(NFData a, NFData b) => NFData (These a b)Defined in these-skinny-0.7.6 · Data.These
type Rep (These a b) = D1 ('MetaData "These" "Data.These" "these-skinny-0.7.6-FLu1Sy6K0CeJFKBs64adWc" 'False) (C1 ('MetaCons "This" 'PrefixI 'False) (S1 ('MetaSel 'Nothing 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)) :+: (C1 ('MetaCons "That" 'PrefixI 'False) (S1 ('MetaSel 'Nothing 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 b)) :+: C1 ('MetaCons "These" 'PrefixI 'False) (S1 ('MetaSel 'Nothing 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a) :*: S1 ('MetaSel 'Nothing 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 b))))Defined in these-skinny-0.7.6 · Data.These

Functions to get rid of These

4 declarations

valuethese :: (a -> c) -> (b -> c) -> (a -> b -> c) -> These a b -> c

Case analysis for the These type.

valuefromThese :: a -> b -> These a b -> (a, b)

Takes two default values and produces a tuple.

valuemergeThese :: (a -> a -> a) -> These a a -> a

Coalesce with the provided operation.

valuemergeTheseWith :: (a -> c) -> (b -> c) -> (c -> c -> c) -> These a b -> c

BiMap and coalesce results with the provided operation.

Traversals

2 declarations

valuehere :: Applicative f => (a -> f b) -> These a t -> f (These b t)

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

valuethere :: Applicative f => (a -> f b) -> These t a -> f (These t b)

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

Case selections

7 declarations

valuejustThis :: These a b -> Maybe a

justThis = preview _This

valuejustThat :: These a b -> Maybe b

justThat = preview _That

valuejustThese :: These a b -> Maybe (a, b)

justThese = preview _These

valuecatThis :: [These a b] -> [a]

Select all This constructors from a list.

valuecatThat :: [These a b] -> [b]

Select all That constructors from a list.

valuecatThese :: [These a b] -> [(a, b)]

Select all These constructors from a list.

valuepartitionThese :: [These a b] -> ([(a, b)], ([a], [b]))

Select each constructor and partition them into separate lists.

Case predicates

3 declarations

valueisThis :: These a b -> Bool

isThis = isJust . justThis

valueisThat :: These a b -> Bool

isThat = isJust . justThat

valueisThese :: These a b -> Bool

isThese = isJust . justThese

Map operations

3 declarations

valuemapThese :: (a -> c) -> (b -> d) -> These a b -> These c d

Bifunctor map.

valuemapThis :: (a -> c) -> These a b -> These c b

mapThis = over here

valuemapThat :: (b -> d) -> These a b -> These a d

mapThat = over there

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