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37 lines
745 B
37 lines
745 B
{-# LANGUAGE RankNTypes #-}
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module Ahc.Data.Lens where
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import Control.Applicative
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import Data.Functor.Identity
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type Lens s t a b = forall f. Functor f => (a -> f b) -> s -> f t
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type Lens' s a = Lens s s a a
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get :: Lens s t a b -> s -> a
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get l = getConst . l Const
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over :: Lens s t a b -> (a -> b) -> s -> t
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over l m = runIdentity . l (Identity . m)
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set :: Lens s t a b -> b -> s -> t
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set l b a = over l (const b) a
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(.~) :: Lens s t a b -> b -> s -> t
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(.~) = set
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infixr 4 .~
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(%~) :: Lens s t a b -> (a -> b) -> s -> t
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(%~) = over
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infixr 4 %~
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(^.) :: s -> Lens s t a b -> a
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x ^. l = get l x
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(&) :: t1 -> (t1 -> t2) -> t2
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x & f = f x
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infixr 0 &
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lens :: (s -> a) -> (s -> b -> t) -> Lens s t a b
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lens sa sbt afb s = sbt s <$> afb (sa s)
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