lib/Hcompta/Lib/Consable.hs

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