src/Rel8/Table/Transpose.hs · rel8

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rel8/src/Rel8/Table/Transpose.hs

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1{-# language DataKinds #-}

2{-# language FlexibleInstances #-}

3{-# language FunctionalDependencies #-}

4{-# language StandaloneKindSignatures #-}

5{-# language TypeFamilies #-}

6{-# language UndecidableInstances #-}

8module Rel8.Table.Transpose

9 ( Transposes

10 )

11where

13-- base

14import Data.Kind ( Constraint, Type )

15import Prelude ()

17-- rel8

18import qualified Rel8.Schema.Kind as K

19import Rel8.Table ( Table, Transpose, Congruent )

22-- | @'Transposes' from to a b@ means that @a@ and @b@ are 'Table's, in the

23-- @from@ and @to@ contexts respectively, which share the same underlying

24-- structure. In other words, @b@ is a version of @a@ transposed from the

25-- @from@ context to the @to@ context (and vice versa).

26type Transposes :: K.Context -> K.Context -> Type -> Type -> Constraint

27class

28 ( Table from a

29 , Table to b

30 , Congruent a b

31 , b ~ Transpose to a

32 , a ~ Transpose from b

33 )

34 => Transposes from to a b

35 | a -> from

36 , b -> to

37 , a to -> b

38 , b from -> a

39instance

40 ( Table from a

41 , Table to b

42 , Congruent a b

43 , b ~ Transpose to a

44 , a ~ Transpose from b

45 )

46 => Transposes from to a b