-- SPDX-FileCopyrightText: 2022 Gregor Kleen <gregor.kleen@ifi.lmu.de>
--
-- SPDX-License-Identifier: AGPL-3.0-or-later

module Utils.NTop
  ( NTop(..)
  ) where

import ClassyPrelude

-- | treat Nothing as Top for Ord (Maybe a); default implementation treats Nothing as bottom
newtype NTop a = NTop { nBot :: a }
  deriving (Read, Show, Generic)
  deriving newtype (Eq)

instance Ord a => Ord (NTop (Maybe a)) where
  compare (NTop Nothing)  (NTop Nothing) = EQ
  compare (NTop Nothing)  _              = GT
  compare _               (NTop Nothing) = LT
  compare (NTop (Just x)) (NTop (Just y)) = compare x y