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oliver-batchelor/Foo.hs

Created August 7, 2019 07:53
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Foo.hs
data ApplyKey b a where
F :: ApplyKey (a -> b)
A :: ApplyKey a
instance Reflex t => Apply (Event t) where
evf <.> evx = fmapMaybe fromDMap e' where
e' merge (DMap.fromList [F :=> evf, A :=> evx])
fromDMap m = case (DMap.lookup F m, DMap.lookup A m) of
(Just (Identity f), Just (Identity a)) -> Just (f a)
_ -> Nothing
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