src/Rel8/Schema/Context/Label.hs · rel8

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1{-# language DataKinds #-}

2{-# language StandaloneKindSignatures #-}

3{-# language TypeFamilies #-}

4{-# language TypeOperators #-}

6module Rel8.Schema.Context.Label

7 ( Labelable( labeler, unlabeler )

8 , HLabelable( hlabeler, hunlabeler )

9 )

10where

12-- base

13import Data.Functor.Identity ( Identity )

14import Data.Kind ( Constraint )

15import Prelude hiding ( null )

17-- rel8

18import Rel8.Schema.Context ( Interpretation, Col(..) )

19import Rel8.Schema.Kind ( Context, HContext )

20import Rel8.Schema.Spec ( Spec( Spec ) )

23type Labelable :: Context -> Constraint

24class Interpretation context => Labelable context where

25 labeler :: ()

26 => Col context ('Spec labels necessity a)

27 -> Col context ('Spec (label ': labels) necessity a)

29 unlabeler :: ()

30 => Col context ('Spec (label ': labels) necessity a)

31 -> Col context ('Spec labels necessity a)

34instance Labelable Identity where

35 labeler (Result a) = Result a

36 unlabeler (Result a) = Result a

39type HLabelable :: HContext -> Constraint

40class HLabelable context where

41 hlabeler :: ()

42 => context ('Spec labels necessity a)

43 -> context ('Spec (label ': labels) necessity a)

45 hunlabeler :: ()

46 => context ('Spec (label ': labels) necessity a)

47 -> context ('Spec labels necessity a)

50instance Labelable context => HLabelable (Col context) where

51 hlabeler = labeler

52 hunlabeler = unlabeler