25 lines
946 B
Haskell
25 lines
946 B
Haskell
{-# OPTIONS_GHC -Wno-orphans #-}
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{-# LANGUAGE
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FlexibleInstances, InstanceSigs, MultiParamTypeClasses, ScopedTypeVariables,
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TypeApplications
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#-}
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module Records (HasField (..)) where
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import GHC.Records
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import GHC.OverloadedLabels
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instance HasField x r a => IsLabel x (r -> a) where
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fromLabel = getField @x
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instance HasField "first" (a, b) a where getField (x, _) = x
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instance HasField "second" (a, b) b where getField (_, y) = y
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instance HasField "first" (a, b, c) a where getField (x, _, _) = x
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instance HasField "second" (a, b, c) b where getField (_, y, _) = y
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instance HasField "third" (a, b, c) c where getField (_, _, z) = z
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instance HasField "first" (a, b, c, d) a where getField (x, _, _, _) = x
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instance HasField "second" (a, b, c, d) b where getField (_, y, _, _) = y
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instance HasField "third" (a, b, c, d) c where getField (_, _, z, _) = z
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instance HasField "fourth" (a, b, c, d) d where getField (_, _, _, w) = w
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