    {-# LANGUAGE ConstraintKinds #-}
    {-# LANGUAGE DataKinds #-}
    {-# LANGUAGE GADTs #-}
    {-# LANGUAGE NoImplicitPrelude #-}
    {-# LANGUAGE PolyKinds #-}
    {-# LANGUAGE Trustworthy #-}
    {-# LANGUAGE StandaloneDeriving #-}
    {-# LANGUAGE StandaloneKindSignatures #-}
    {-# LANGUAGE TypeFamilies #-}
    {-# LANGUAGE TypeOperators #-}
    {-# LANGUAGE UndecidableInstances #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  GHC.Internal.Data.Type.Ord
    -- License     :  BSD-style (see the LICENSE file in the distribution)
    --
    -- Maintainer  :  libraries@haskell.org
    -- Stability   :  stable
    -- Portability :  not portable
    --
    -- Basic operations on type-level Orderings.
    --
    -- @since base-4.16.0.0
    -----------------------------------------------------------------------------

    module GHC.Internal.Data.Type.Ord (
      Compare, OrderingI(..)
      , type (<=), type (<=?)
      , type (>=), type (>=?)
      , type (>), type (>?)
      , type (<), type (<?)
      , Max, Min
      , OrdCond
      ) where

    import GHC.Internal.Show(Show(..))
    import GHC.Internal.TypeError
    import GHC.Internal.TypeLits.Internal
    import GHC.Internal.TypeNats.Internal
    import GHC.Internal.Types (type (~), Char)
    import GHC.Internal.Data.Bool
    import GHC.Internal.Data.Eq
    import GHC.Internal.Data.Ord

    -- | 'Compare' branches on the kind of its arguments to either compare by
    -- 'Symbol' or 'Nat'.
    --
    -- @since base-4.16.0.0
    type Compare :: k -> k -> Ordering
    type family Compare (a :: k) (b :: k) :: Ordering

    type instance Compare (a :: Natural) b = CmpNat    a b
    type instance Compare (a :: Symbol)  b = CmpSymbol a b
    type instance Compare (a :: Char)    b = CmpChar   a b

    -- | Ordering data type for type literals that provides proof of their ordering.
    --
    -- @since base-4.16.0.0
    data OrderingI a b where
      LTI :: Compare a b ~ 'LT => OrderingI a b
      EQI :: Compare a a ~ 'EQ => OrderingI a a
      GTI :: Compare a b ~ 'GT => OrderingI a b

    deriving instance Show (OrderingI a b)
    deriving instance Eq   (OrderingI a b)

    infix 4 <=?, <=, >=?, >=, <?, <, >?, >

    -- | Comparison (<=) of comparable types, as a constraint.
    --
    -- @since base-4.16.0.0
    type x <= y = Assert (x <=? y) (LeErrMsg x y)
    type LeErrMsg x y = TypeError ('Text "Cannot satisfy: " ':<>: 'ShowType x ':<>: 'Text " <= " ':<>: 'ShowType y)

    -- | Comparison (>=) of comparable types, as a constraint.
    --
    -- @since base-4.16.0.0
    type x >= y = Assert (x >=? y) (GeErrMsg x y)
    type GeErrMsg x y = TypeError ('Text "Cannot satisfy: " ':<>: 'ShowType x ':<>: 'Text " >= " ':<>: 'ShowType y)

    -- | Comparison (<) of comparable types, as a constraint.
    --
    -- @since base-4.16.0.0
    type x < y = Assert (x <? y) (LtErrMsg x y)
    type LtErrMsg x y = TypeError ('Text "Cannot satisfy: " ':<>: 'ShowType x ':<>: 'Text " < " ':<>: 'ShowType y)

    -- | Comparison (>) of comparable types, as a constraint.
    --
    -- @since base-4.16.0.0
    type x > y = Assert (x >? y) (GtErrMsg x y)
    type GtErrMsg x y = TypeError ('Text "Cannot satisfy: " ':<>: 'ShowType x ':<>: 'Text " > " ':<>: 'ShowType y)

    -- | Comparison (<=) of comparable types, as a function.
    --
    -- @since base-4.16.0.0
    type (<=?) :: k -> k -> Bool
    type m <=? n = OrdCond (Compare m n) 'True 'True 'False

    -- | Comparison (>=) of comparable types, as a function.
    --
    -- @since base-4.16.0.0
    type (>=?) :: k -> k -> Bool
    type m >=? n = OrdCond (Compare m n) 'False 'True 'True

    -- | Comparison (<) of comparable types, as a function.
    --
    -- @since base-4.16.0.0
    type (<?) :: k -> k -> Bool
    type m <? n = OrdCond (Compare m n) 'True 'False 'False

    -- | Comparison (>) of comparable types, as a function.
    --
    -- @since base-4.16.0.0
    type (>?) :: k -> k -> Bool
    type m >? n = OrdCond (Compare m n) 'False 'False 'True

    -- | Maximum between two comparable types.
    --
    -- @since base-4.16.0.0
    type Max :: k -> k -> k
    type Max m n = OrdCond (Compare m n) n n m

    -- | Minimum between two comparable types.
    --
    -- @since base-4.16.0.0
    type Min :: k -> k -> k
    type Min m n = OrdCond (Compare m n) m m n

    -- | A case statement on 'Ordering'.
    --
    -- @OrdCond c l e g@ is @l@ when @c ~ LT@, @e@ when @c ~ EQ@, and @g@ when
    -- @c ~ GT@.
    --
    -- @since base-4.16.0.0
    type OrdCond :: Ordering -> k -> k -> k -> k
    type family OrdCond o lt eq gt where
      OrdCond 'LT lt eq gt = lt
      OrdCond 'EQ lt eq gt = eq
      OrdCond 'GT lt eq gt = gt