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 )

19import Rel8.Expr.Array ( sappend1 )

20import Rel8.Schema.Context ( Col, Col'(..) )

21import Rel8.Schema.HTable.NonEmpty ( HNonEmptyTable )

22import Rel8.Schema.HTable.Vectorize ( happend )

23import Rel8.Table ( Table, Context, Columns, fromColumns, toColumns )

24import Rel8.Table.Alternative ( AltTable, (<|>:) )

25import Rel8.Table.Recontextualize ( Recontextualize )

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

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

30type NonEmptyTable :: Type -> Type

31newtype NonEmptyTable a =

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

35instance Table context a => Table context (NonEmptyTable a) where

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

37 type Context (NonEmptyTable a) = Context a

39 fromColumns = NonEmptyTable

40 toColumns (NonEmptyTable a) = a

43instance Recontextualize from to a b =>

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

47instance AltTable NonEmptyTable where

48 (<|>:) = (<>)

51instance Table Expr a => Semigroup (NonEmptyTable a) where

52 NonEmptyTable as <> NonEmptyTable bs = NonEmptyTable $

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