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Define sequenceAlt generically.

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Rob Rix 2018-04-09 16:26:49 -04:00
parent 4459b26b0b
commit ebe142e263
1 changed files with 15 additions and 1 deletions
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src/Data/Mergeable.hs
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@ -27,7 +27,8 @@ class Functor t => Mergeable t where
-- | Sequnce a 'Mergeable' functor by 'merge'ing the 'Alternative' values.
sequenceAlt :: Alternative f => t (f a) -> f (t a)
sequenceAlt = merge id
default sequenceAlt :: (Generic1 t, GMergeable (Rep1 t), Alternative f) => t (f a) -> f (t a)
sequenceAlt = genericSequenceAlt
-- Instances
@ -48,37 +49,50 @@ instance Mergeable Identity where merge f = fmap Identity . f . runIdentity
instance (Apply Functor fs, Apply Mergeable fs) => Mergeable (Union fs) where
merge f = apply' (Proxy :: Proxy Mergeable) (\ reinj g -> reinj <$> merge f g)
sequenceAlt = apply' (Proxy :: Proxy Mergeable) (\ inj t -> inj <$> sequenceAlt t)
-- Generics
class GMergeable t where
gmerge :: Alternative f => (a -> f b) -> t a -> f (t b)
gsequenceAlt :: Alternative f => t (f a) -> f (t a)
genericMerge :: (Generic1 t, GMergeable (Rep1 t), Alternative f) => (a -> f b) -> t a -> f (t b)
genericMerge f = fmap to1 . gmerge f . from1
genericSequenceAlt :: (Generic1 t, GMergeable (Rep1 t), Alternative f) => t (f a) -> f (t a)
genericSequenceAlt = fmap to1 . gsequenceAlt . from1
-- Instances
instance GMergeable U1 where
gmerge _ _ = pure U1
gsequenceAlt _ = pure U1
instance GMergeable Par1 where
gmerge f (Par1 a) = Par1 <$> f a
gsequenceAlt (Par1 a) = Par1 <$> a
instance GMergeable (K1 i c) where
gmerge _ (K1 a) = pure (K1 a)
gsequenceAlt (K1 a) = pure (K1 a)
instance Mergeable f => GMergeable (Rec1 f) where
gmerge f (Rec1 a) = Rec1 <$> merge f a
gsequenceAlt (Rec1 a) = Rec1 <$> sequenceAlt a
instance GMergeable f => GMergeable (M1 i c f) where
gmerge f (M1 a) = M1 <$> gmerge f a
gsequenceAlt (M1 a) = M1 <$> gsequenceAlt a
instance (GMergeable f, GMergeable g) => GMergeable (f :+: g) where
gmerge f (L1 a) = L1 <$> gmerge f a
gmerge f (R1 b) = R1 <$> gmerge f b
gsequenceAlt (L1 a) = L1 <$> gsequenceAlt a
gsequenceAlt (R1 a) = R1 <$> gsequenceAlt a
instance (GMergeable f, GMergeable g) => GMergeable (f :*: g) where
gmerge f (a :*: b) = (:*:) <$> gmerge f a <*> gmerge f b
gsequenceAlt (a :*: b) = (:*:) <$> gsequenceAlt a <*> gsequenceAlt b