-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/
-- | Type-level Ord compatibility layer
--
-- In base-4.16.0.0, an open type family Compare was
-- added as a type-level analog of Ord. This package provides a
-- compatible interface on earlier versions of base, and
-- re-exports the canonical one with later versions.
@package type-compare
@version 0.1.1
-- | Type-level Ord.
--
-- On recent versions of base, this just re-exports things from
-- Data.Type.Ord. On older versions, it provides its own
-- implementation, moved from older versions of numeric-kinds.
module Kinds.Ord
-- | Type-level Ord "kindclass".
--
-- Note this has an invisible dependent k parameter that makes
-- the textually-identical instances for different kinds actually
-- different. Neat!
type family Compare (x :: k) (y :: k) :: Ordering
type x =? y = CompareCond x y False True True
infix 4 >=?
type x >? y = CompareCond x y False False True
infix 4 >?
type x < y = Proven (x = y = Proven (x >=? y)
infix 4 >=
type x > y = Proven (x >? y)
infix 4 >
type Max x y = CompareCond x y y y x
type Min x y = CompareCond x y x x y
-- | Ordering results carrying evidence of type-level ordering relations.
data OrderingI m n
[LTI] :: Compare m n ~ 'LT => OrderingI m n
[EQI] :: Compare m m ~ 'EQ => OrderingI m m
[GTI] :: Compare m n ~ 'GT => OrderingI m n
-- | Turns a type-level Bool into a Constraint that it's
-- True.
type Proven b = b ~ 'True
-- | Type-level eliminator for Ordering.
--
-- OrdCond o lt eq gt selects from among lt,
-- eq, and gt according to o.
type family OrdCond (o :: Ordering) (lt :: k) (eq :: k) (gt :: k) :: k
-- | CompareCond x y lt eq gt is lt if x is less
-- than y, and so on.
type CompareCond x y lt eq gt = OrdCond (Compare x y) lt eq gt