src/Rel8/Order.hs · rel8

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rel8/src/Rel8/Order.hs

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1{-# language DerivingStrategies #-}

2{-# language GeneralizedNewtypeDeriving #-}

3{-# language StandaloneKindSignatures #-}

5module Rel8.Order

6 ( Order(..)

7 )

8where

10-- base

11import Data.Functor.Contravariant ( Contravariant )

12import Data.Kind ( Type )

13import Prelude

15-- contravariant

16import Data.Functor.Contravariant.Divisible ( Decidable, Divisible )

18-- opaleye

19import qualified Opaleye.Order as Opaleye

22-- | An ordering expression for @a@. Primitive orderings are defined with

23-- 'Rel8.asc' and 'Rel8.desc', and you can combine @Order@ via its various

24-- instances.

26-- A common pattern is to use '<>' to combine multiple orderings in sequence,

27-- and 'Data.Functor.Contravariant.>$<' to select individual columns.

28type Order :: Type -> Type

29newtype Order a = Order (Opaleye.Order a)

30 deriving newtype (Contravariant, Divisible, Decidable, Semigroup, Monoid)