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-- |
-- Module : Basement.These
-- License : BSD-style
-- Maintainer : Nicolas Di Prima <nicolas@primetype.co.uk>
-- Stability : stable
-- Portability : portable
--
-- @These a b@, sum type to represent either @a@ or @b@ or both.
--
module Basement.These
( These(..)
) where
import Basement.Compat.Base
import Basement.NormalForm
-- | Either a or b or both.
data These a b
= This a
| That b
| These a b
deriving (Eq, Ord, Show, Typeable)
instance (NormalForm a, NormalForm b) => NormalForm (These a b) where
toNormalForm (This a) = toNormalForm a
toNormalForm (That b) = toNormalForm b
toNormalForm (These a b) = toNormalForm a `seq` toNormalForm b
|
