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{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FlexibleContexts #-}
module T2715 where
data Interval v where
Intv :: (Ord v, Enum v) => (v,v) -> Interval v
type family Domain (d :: * -> *) :: * -> *
type instance Domain Interval = Interval
type family Value (d :: * -> *) :: *
class IDomain d where
empty :: (Ord (Value d), Enum (Value d)) => (Domain d) (Value d)
class (IDomain d1) -- (IDomain d1, IDomain d2, Value d1 ~ Value d2)
=> IIDomain (d1 :: * -> *) (d2 :: * -> * ) where
equals :: Domain d1 (Value d1) -> Domain d2 (Value d2) -> Bool
instance Ord (Value Interval)
=> IDomain Interval where
empty = Intv (toEnum 1, toEnum 0)
instance Ord (Value Interval)
=> IIDomain Interval Interval where
equals (Intv ix) (Intv iy) = ix == iy
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