src/Rel8/Query/Filter.hs · rel8

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rel8/src/Rel8/Query/Filter.hs

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1module Rel8.Query.Filter

2 ( filter

3 , where_

4 )

5where

7-- base

8import Prelude hiding ( filter )

10-- opaleye

11import qualified Opaleye.Operators as Opaleye

13-- profunctors

14import Data.Profunctor ( lmap )

16-- rel8

17import Rel8.Expr ( Expr )

18import Rel8.Expr.Opaleye ( toColumn, toPrimExpr )

19import Rel8.Query ( Query )

20import Rel8.Query.Opaleye ( fromOpaleye )

23filter :: (a -> Expr Bool) -> a -> Query a

24filter f a = a <$ where_ (f a)

27where_ :: Expr Bool -> Query ()

28where_ condition =

29 fromOpaleye $ lmap (\_ -> toColumn $ toPrimExpr condition) Opaleye.restrict