src/Rel8/Column.hs · rel8

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rel8/src/Rel8/Column.hs

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1{-# language DataKinds #-}

2{-# language TypeFamilies #-}

3{-# language StandaloneKindSignatures #-}

5module Rel8.Column

6 ( Column, Default

7 , TColumn

8 )

9where

11-- base

12import Data.Kind ( Type )

13import Prelude ()

15-- rel8

16import Rel8.Column.Field ( Field )

17import Rel8.FCF ( Eval, Exp )

18import Rel8.Kind.Necessity ( Necessity( Required, Optional ) )

19import qualified Rel8.Schema.Kind as K

22-- | The @Column@ type family should be used to indicate which fields of your

23-- data types are single columns in queries. This type family has special

24-- support when a query is executed, allowing you to use a single data type for

25-- both query data and rows decoded to Haskell.

26type Column :: K.Context -> Type -> Type

27type Column context a = Field context 'Required a

30type Default :: K.Context -> Type -> Type

31type Default context a = Field context 'Optional a

34data TColumn :: K.Context -> Type -> Exp Type

35type instance Eval (TColumn f a) = Column f a