23 lines
467 B
Haskell
23 lines
467 B
Haskell
module Lets.Lens.Profunctor
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(
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Profunctor(dimap)
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) where
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import Lets.Data
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-- | A profunctor is a binary functor, with the first argument in contravariant
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-- (negative) position and the second argument in covariant (positive) position.
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class Profunctor p where
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dimap ::
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(b -> a)
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-> (c -> d)
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-> p a c
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-> p b d
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instance Profunctor (->) where
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dimap f g = \h -> g . h . f
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instance Profunctor Tagged where
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dimap _ g (Tagged x) =
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Tagged (g x)
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