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jmatsushita/Main.purs

Last active October 14, 2021 18:45
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Existential types with constraints
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Main.purs
module Main where
import Prelude
newtype AnyShow = AnyShow (forall r. (forall a. Show a => a -> r) -> r)
mkAnyShow :: forall a. Show a => a -> AnyShow
mkAnyShow a = AnyShow (_ $ a)
elimAnyShow :: forall r. (forall a. Show a => a -> r) -> AnyShow -> r
elimAnyShow f (AnyShow a) = f a
instance Show AnyShow where
show (AnyShow a) = a show
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