src/Rel8/Column/NonEmpty.hs · rel8

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rel8/src/Rel8/Column/NonEmpty.hs

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1{-# language DataKinds #-}

2{-# language StandaloneKindSignatures #-}

3{-# language TypeFamilyDependencies #-}

5module Rel8.Column.NonEmpty

6 ( HNonEmpty

7 )

8where

10-- base

11import Data.Kind ( Type )

12import Data.List.NonEmpty ( NonEmpty )

13import Prelude ()

15-- rel8

16import Rel8.Aggregate ( Aggregate )

17import Rel8.Expr ( Expr )

18import qualified Rel8.Schema.Kind as K

19import Rel8.Schema.Name ( Name )

20import Rel8.Schema.Result ( Result )

21import Rel8.Table.NonEmpty ( NonEmptyTable )

24-- | Nest a 'NonEmpty' list within a 'Rel8able'. @HNonEmpty f a@ will produce a

25-- 'NonEmptyTable' @a@ in the 'Expr' context, and a 'NonEmpty' @a@ in the

26-- 'Result' context.

27type HNonEmpty :: K.Context -> Type -> Type

28type family HNonEmpty context = nonEmpty | nonEmpty -> context where

29 HNonEmpty Aggregate = NonEmptyTable Aggregate

30 HNonEmpty Expr = NonEmptyTable Expr

31 HNonEmpty Name = NonEmptyTable Name

32 HNonEmpty Result = NonEmpty