src/Rel8/Type/Sum.hs · rel8

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1{-# language DataKinds #-}

2{-# language FlexibleContexts #-}

3{-# language FlexibleInstances #-}

4{-# language MultiParamTypeClasses #-}

5{-# language TypeFamilies #-}

6{-# language StandaloneKindSignatures #-}

7{-# language UndecidableInstances #-}

9module Rel8.Type.Sum

10 ( DBSum

11 )

12where

14-- base

15import Data.Int ( Int16, Int32, Int64 )

16import Data.Kind ( Constraint, Type )

17import Prelude

19-- rel8

20import Rel8.Schema.Nullability ( HasNullability, Unnullify, Sql )

21import Rel8.Type ( DBType )

23-- scientific

24import Data.Scientific ( Scientific )

26-- time

27import Data.Time.LocalTime ( CalendarDiffTime )

30-- | The class of database types that support the @sum()@ aggregation function.

31type DBSum :: Type -> Constraint

32class DBType a => DBSum a

33instance DBSum Int16

34instance DBSum Int32

35instance DBSum Int64

36instance DBSum Float

37instance DBSum Double

38instance DBSum Scientific

39instance DBSum CalendarDiffTime

42instance {-# INCOHERENT #-} (HasNullability a, DBSum (Unnullify a)) =>

43 Sql DBSum a