src/Rel8/Schema/HTable/Maybe.hs · rel8

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1{-# language DataKinds #-}

2{-# language DeriveAnyClass #-}

3{-# language DeriveGeneric #-}

4{-# language DerivingStrategies #-}

5{-# language FlexibleInstances #-}

6{-# language StandaloneKindSignatures #-}

7{-# language UndecidableInstances #-}

8{-# language UndecidableSuperClasses #-}

10module Rel8.Schema.HTable.Maybe

11 ( HMaybeTable(..)

12 , HMaybeNullifiable

13 )

14where

16-- base

17import Data.Kind ( Constraint )

18import GHC.Generics ( Generic )

19import Prelude

21-- rel8

22import Rel8.Kind.Necessity ( Necessity( Required ) )

23import Rel8.Schema.Context.Nullify ( HConstrainTag, HNullifiable )

24import Rel8.Schema.HTable ( HTable )

25import Rel8.Schema.HTable.Identity ( HIdentity(..) )

26import qualified Rel8.Schema.Kind as K

27import Rel8.Schema.Spec ( Spec( Spec ) )

28import Rel8.Type.Tag ( MaybeTag )

29import Rel8.Schema.HTable.Nullify ( HNullify )

32type HMaybeTable :: K.HTable -> K.HTable

33data HMaybeTable table context = HMaybeTable

34 { htag :: HIdentity ('Spec '["isJust"] 'Required (Maybe MaybeTag)) context

35 , hjust :: HNullify table context

36 }

37 deriving stock Generic

38 deriving anyclass HTable

41type HMaybeNullifiable :: K.HContext -> Constraint

42class (HNullifiable context, HConstrainTag context MaybeTag) => HMaybeNullifiable context

43instance (HNullifiable context, HConstrainTag context MaybeTag) => HMaybeNullifiable context