lib/Hcompta/Lib/Consable.hs

   1 {-# LANGUAGE FlexibleContexts #-}
   2 {-# LANGUAGE FlexibleInstances #-}
   3 {-# LANGUAGE MultiParamTypeClasses #-}
   4 {-# OPTIONS_GHC -fno-warn-orphans #-}
   5
   6 module Hcompta.Lib.Consable where
   7
   8 --import           Control.Applicative (Const(..))
   9 import           Data.Functor.Compose (Compose(..))
  10 import           Data.Monoid ()
  11
  12 class Monoid (xs x) => Consable context xs x where
  13         mcons :: context -> x -> xs x -> xs x
  14
  15 instance Monoid (f (g x)) => Monoid ((Compose f g) x) where
  16         mempty = Compose mempty
  17         mappend (Compose x) (Compose y) = Compose $ mappend x y