src/Rel8/Schema/Field.hs · rel8

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1{-# language DataKinds #-}

2{-# language FlexibleContexts #-}

3{-# language MultiParamTypeClasses #-}

4{-# language StandaloneKindSignatures #-}

5{-# language TypeFamilies #-}

7module Rel8.Schema.Field

8 ( Field(..)

9 , fields

10 )

11where

13-- base

14import Data.Functor.Identity ( Identity( Identity ) )

15import Data.Kind ( Type )

16import Prelude

18-- rel8

19import Rel8.Schema.HTable ( HField, htabulate )

20import Rel8.Schema.HTable.Identity ( HIdentity( HIdentity ) )

21import Rel8.Schema.Kind as K

22import Rel8.Schema.Null ( Sql )

23import Rel8.Table

24 ( Table, Columns, Context, fromColumns, toColumns

25 , FromExprs, fromResult, toResult

26 , Transpose

27 )

28import Rel8.Table.Transpose ( Transposes )

29import Rel8.Type ( DBType )

32-- | A special context used in the construction of 'Rel8.Projection's.

33type Field :: Type -> K.Context

34newtype Field table a = Field (HField (Columns table) a)

37instance Sql DBType a => Table (Field table) (Field table a) where

38 type Columns (Field table a) = HIdentity a

39 type Context (Field table a) = Field table

40 type FromExprs (Field table a) = a

41 type Transpose to (Field table a) = to a

43 toColumns = HIdentity

44 fromColumns (HIdentity a) = a

45 toResult a = HIdentity (Identity a)

46 fromResult (HIdentity (Identity a)) = a

49fields :: Transposes context (Field table) table fields => fields

50fields = fromColumns $ htabulate Field