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Garciat/PatternFail.hs

Created May 14, 2021 11:29
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PatternFail.hs
import Control.Exception
import System.IO.Unsafe
match :: (a -> b) -> a -> Maybe b
match m a = unsafeDupablePerformIO $
handle (\(PatternMatchFail _) -> pure Nothing) $ do
x <- evaluate (m a)
return (Just x)
what :: Either a b -> Maybe b
what = match (\case Right x -> x)
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