src/Rel8/Column/These.hs · rel8

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1{-# language DataKinds #-}

2{-# language StandaloneKindSignatures #-}

3{-# language TypeFamilyDependencies #-}

5module Rel8.Column.These

6 ( HThese

7 )

8where

10-- base

11import Data.Kind ( Type )

12import Prelude ()

14-- rel8

15import Rel8.Aggregate ( Aggregate )

16import Rel8.Expr ( Expr )

17import qualified Rel8.Schema.Kind as K

18import Rel8.Schema.Name ( Name )

19import Rel8.Schema.Result ( Result )

20import Rel8.Table.These ( TheseTable )

22-- these

23import Data.These ( These )

26-- | Nest an 'These' value within a 'Rel8able'. @HThese f a b@ will produce a

27-- 'TheseTable' @a b@ in the 'Expr' context, and a 'These' @a b@ in the

28-- 'Result' context.

29type HThese :: K.Context -> Type -> Type -> Type

30type family HThese context = these | these -> context where

31 HThese Aggregate = TheseTable Aggregate

32 HThese Expr = TheseTable Expr

33 HThese Name = TheseTable Name

34 HThese Result = These