src/Rel8/Table/NonEmpty.hs · rel8

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rel8/src/Rel8/Table/NonEmpty.hs

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1{-# language FlexibleInstances #-}

2{-# language MultiParamTypeClasses #-}

3{-# language StandaloneKindSignatures #-}

4{-# language TypeFamilies #-}

5{-# language UndecidableInstances #-}

7module Rel8.Table.NonEmpty

8 ( NonEmptyTable(..)

9 , HNonEmptyTable

10 )

11where

13-- base

14import Data.Kind ( Type )

15import Prelude

17-- rel8

18import Rel8.Expr ( Expr, Col(..) )

19import Rel8.Expr.Array ( sappend1 )

20import Rel8.Schema.HTable.NonEmpty ( HNonEmptyTable )

21import Rel8.Schema.HTable.Vectorize ( happend )

22import Rel8.Table ( Table, Context, Columns, fromColumns, toColumns )

23import Rel8.Table.Alternative ( AltTable, (<|>:) )

24import Rel8.Table.Recontextualize ( Recontextualize )

27-- | A @NonEmptyTable@ value contains one or more instances of @a@. You

28-- construct @NonEmptyTable@s with 'some' or 'nonEmptyAgg'.

29type NonEmptyTable :: Type -> Type

30newtype NonEmptyTable a =

31 NonEmptyTable (HNonEmptyTable (Columns a) (Col (Context a)))

34instance Table context a => Table context (NonEmptyTable a) where

35 type Columns (NonEmptyTable a) = HNonEmptyTable (Columns a)

36 type Context (NonEmptyTable a) = Context a

38 fromColumns = NonEmptyTable

39 toColumns (NonEmptyTable a) = a

42instance Recontextualize from to a b =>

43 Recontextualize from to (NonEmptyTable a) (NonEmptyTable b)

46instance AltTable NonEmptyTable where

47 (<|>:) = (<>)

50instance Table Expr a => Semigroup (NonEmptyTable a) where

51 NonEmptyTable as <> NonEmptyTable bs = NonEmptyTable $

52 happend (\_ _ (DB a) (DB b) -> DB (sappend1 a b)) as bs