src/Rel8/Table/Cols.hs · rel8

on 379b492 help sign in

50 lines 1.2 kB history raw

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(..) )

26type Cols :: K.Context -> K.HTable -> Type

27newtype Cols context columns = Cols (columns context)

30instance (HTable columns, context ~ context') =>

31 Table context' (Cols context columns)

32 where

33 type Columns (Cols context columns) = columns

34 type Context (Cols context columns) = context

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

36 type Transpose to (Cols context columns) = Cols to columns

38 toColumns (Cols a) = a

39 fromColumns = Cols

41 toResult (Cols a) = a

42 fromResult = Cols

45fromCols :: Table context a => Cols context (Columns a) -> a

46fromCols (Cols a) = fromColumns a

49toCols :: Table context a => a -> Cols context (Columns a)

50toCols = Cols . toColumns