Safe Haskell | Safe |
---|---|
Language | Haskell2010 |
The These
type and associated operations. Now enhanced with Control.Lens magic!
Synopsis
- data 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
- partitionThese :: [These a b] -> ([a], [b], [(a, b)])
- partitionHereThere :: [These a b] -> ([a], [b])
- partitionEithersNE :: NonEmpty (Either a b) -> These (NonEmpty a) (NonEmpty b)
- distrThesePair :: These (a, b) c -> (These a c, These b c)
- undistrThesePair :: (These a c, These b c) -> These (a, b) c
- distrPairThese :: (These a b, c) -> These (a, c) (b, c)
- undistrPairThese :: These (a, c) (b, c) -> (These a b, c)
Documentation
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
represents These
A B(A + B + AB)
, which doesn't factor easily into
sums and products--a type like
is unclear and
awkward to use.Either
A (B, Maybe
A)
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.
Instances
Bifunctor These Source # | |
Swap These Source # | Since: 0.8 |
Defined in Data.These | |
Assoc These Source # | Since: 0.8 |
Bitraversable These Source # | |
Defined in Data.These bitraverse :: Applicative f => (a -> f c) -> (b -> f d) -> These a b -> f (These c d) # | |
Bifoldable These Source # | |
Eq2 These Source # | Since: 1.1.1 |
Ord2 These Source # | Since: 1.1.1 |
Defined in Data.These | |
Read2 These Source # | Since: 1.1.1 |
Defined in Data.These liftReadsPrec2 :: (Int -> ReadS a) -> ReadS [a] -> (Int -> ReadS b) -> ReadS [b] -> Int -> ReadS (These a b) # liftReadList2 :: (Int -> ReadS a) -> ReadS [a] -> (Int -> ReadS b) -> ReadS [b] -> ReadS [These a b] # liftReadPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec (These a b) # liftReadListPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec [These a b] # | |
Show2 These Source # | Since: 1.1.1 |
NFData2 These Source # | Since: 1.1.1 |
Defined in Data.These | |
Hashable2 These Source # | Since: 1.1.1 |
Defined in Data.These | |
Semigroup a => Monad (These a) Source # | |
Functor (These a) Source # | |
Semigroup a => Applicative (These a) Source # | |
Foldable (These a) Source # | |
Defined in Data.These 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] # elem :: Eq a0 => a0 -> These a a0 -> Bool # maximum :: Ord a0 => These a a0 -> a0 # minimum :: Ord a0 => These a a0 -> a0 # | |
Traversable (These a) Source # | |
Eq a => Eq1 (These a) Source # | Since: 1.1.1 |
Ord a => Ord1 (These a) Source # | Since: 1.1.1 |
Defined in Data.These | |
Read a => Read1 (These a) Source # | Since: 1.1.1 |
Defined in Data.These | |
Show a => Show1 (These a) Source # | Since: 1.1.1 |
NFData a => NFData1 (These a) Source # | Since: 1.1.1 |
Defined in Data.These | |
Hashable a => Hashable1 (These a) Source # | Since: 1.1.1 |
Defined in Data.These | |
Generic1 (These a :: Type -> Type) Source # | |
(Eq a, Eq b) => Eq (These a b) Source # | |
(Data a, Data b) => Data (These a b) Source # | |
Defined in Data.These 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 # | |
Defined in Data.These | |
(Read a, Read b) => Read (These a b) Source # | |
(Show a, Show b) => Show (These a b) Source # | |
Generic (These a b) Source # | |
(Semigroup a, Semigroup b) => Semigroup (These a b) Source # | |
(Binary a, Binary b) => Binary (These a b) Source # | Since: 0.7.1 |
(NFData a, NFData b) => NFData (These a b) Source # | Since: 0.7.1 |
Defined in Data.These | |
(Hashable a, Hashable b) => Hashable (These a b) Source # | |
Defined in Data.These | |
type Rep1 (These a :: Type -> Type) Source # | |
Defined in Data.These type Rep1 (These a :: Type -> Type) = D1 (MetaData "These" "Data.These" "these-1.1.1-7oOR7gP5PVbK4wJ2RcKP8p" 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) Par1) :+: C1 (MetaCons "These" PrefixI False) (S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 a) :*: S1 (MetaSel (Nothing :: Maybe Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) Par1))) | |
type Rep (These a b) Source # | |
Defined in Data.These type Rep (These a b) = D1 (MetaData "These" "Data.These" "these-1.1.1-7oOR7gP5PVbK4wJ2RcKP8p" 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.
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.
Partition
partitionThese :: [These a b] -> ([a], [b], [(a, b)]) Source #
Select each constructor and partition them into separate lists.
partitionHereThere :: [These a b] -> ([a], [b]) Source #
Select here
and there
elements and partition them into separate lists.
Since: 0.8
partitionEithersNE :: NonEmpty (Either a b) -> These (NonEmpty a) (NonEmpty b) Source #
Like partitionEithers
but for NonEmpty
types.
Note: this is not online algorithm. In the worst case it will traverse the whole list before deciding the result constructor.
>>>
partitionEithersNE $ Left 'x' :| [Right 'y']
These ('x' :| "") ('y' :| "")
>>>
partitionEithersNE $ Left 'x' :| map Left "yz"
This ('x' :| "yz")
Since: 1.0.1
Distributivity
This distributivity combinators aren't isomorphisms!
distrPairThese :: (These a b, c) -> These (a, c) (b, c) Source #
undistrPairThese :: These (a, c) (b, c) -> (These a b, c) Source #