src/Rel8/Column/List.hs · rel8

on 97d89cf help sign in

30 lines 787 B history raw

1{-# language DataKinds #-}

2{-# language StandaloneKindSignatures #-}

3{-# language TypeFamilyDependencies #-}

5module Rel8.Column.List

6 ( HList

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.List ( ListTable )

23-- | Nest a list within a 'Rel8able'. @HList f a@ will produce a 'ListTable'

24-- @a@ in the 'Expr' context, and a @[a]@ in the 'Result' context.

25type HList :: K.Context -> Type -> Type

26type family HList context = list | list -> context where

27 HList Aggregate = ListTable Aggregate

28 HList Expr = ListTable Expr

29 HList Name = ListTable Name

30 HList Result = []