src/Rel8/Table/Cols.hs · rel8

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1{-# language DataKinds #-}

2{-# language FlexibleInstances #-}

3{-# language MultiParamTypeClasses #-}

4{-# language StandaloneKindSignatures #-}

5{-# language TypeFamilies #-}

6{-# language UndecidableInstances #-}

8module Rel8.Table.Cols

9 ( Cols( Cols )

10 , fromCols

11 , toCols

12 )

13where

15-- base

16import Data.Kind ( Type )

17import Prelude

19-- rel8

20import qualified Rel8.Schema.Kind as K

21import Rel8.Schema.HTable ( HTable )

22import Rel8.Schema.Result ( Result )

23import Rel8.Table ( Table(..) )

24import Rel8.Table.Recontextualize ( Recontextualize )

27type Cols :: K.Context -> K.HTable -> Type

28newtype Cols context columns = Cols (columns context)

31instance (HTable columns, context ~ context') =>

32 Table context' (Cols context columns)

33 where

34 type Columns (Cols context columns) = columns

35 type Context (Cols context columns) = context

36 type FromExprs (Cols context columns) = Cols Result columns

38 toColumns (Cols a) = a

39 fromColumns = Cols

41 toResult (Cols a) = a

42 fromResult = Cols

45instance HTable t => Recontextualize from to (Cols from t) (Cols to t)

48fromCols :: Table context a => Cols context (Columns a) -> a

49fromCols (Cols a) = fromColumns a

52toCols :: Table context a => a -> Cols context (Columns a)

53toCols = Cols . toColumns