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Created September 27, 2020 00:36
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z.hs
{-# LANGUAGE ExplicitForAll, TypeApplications, ScopedTypeVariables #-}
import Control.Monad.Except
import Data.Coerce
import Data.Functor.Identity
maybeToEither :: e -> Maybe a -> Either e a
maybeToEither v m = case m of
Nothing -> Left v
Just r -> Right r
m2e :: forall e a. e -> Maybe a -> Except e a
m2e = coerce (maybeToEither @e @a)
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