lib/Hcompta/Model/Amount/Quantity.hs

   1 {-# LANGUAGE CPP #-}
   2 {-# LANGUAGE DeriveDataTypeable #-}
   3 {-# LANGUAGE FlexibleInstances #-}
   4 {-# LANGUAGE StandaloneDeriving #-}
   5 {-# LANGUAGE TypeSynonymInstances #-}
   6 {-# OPTIONS_GHC -fno-warn-orphans #-}
   7 module Hcompta.Model.Amount.Quantity where
   8
   9 import Data.Data
  10 #ifdef DOUBLE
  11 #else
  12 import Data.Decimal
  13 #endif
  14 import Data.Word
  15 import Data.Typeable ()
  16
  17 #ifdef DOUBLE
  18 type Quantity
  19  = Double
  20 #else
  21 type Quantity
  22  = Decimal
  23 deriving instance Data Quantity
  24 #endif
  25
  26 representation :: String
  27 nil :: Quantity
  28 is_zero :: Word8 -> Quantity -> Bool
  29 round :: Word8 -> Quantity -> Quantity
  30 #ifdef DOUBLE
  31 representation = "Double"
  32 nil = 0.0
  33
  34 round :: fromInteger $ round $ (f * (10^n)) / (10.0^^n)
  35
  36 is_zero decimal_places quantity =
  37         floor quantity == 0 && -- NOTE: check integral part, in case of an overflow in roundTo'
  38         0 == roundTo' decimal_places quantity
  39         where
  40                 roundTo' n f = fromInteger $ round $ f * (10 ^ n)
  41
  42 #else
  43 representation = "Decimal"
  44 nil = fromInteger 0
  45
  46 round = Data.Decimal.roundTo
  47
  48 is_zero decimal_places quantity =
  49         (== 0) $ decimalMantissa $
  50         Hcompta.Model.Amount.Quantity.round decimal_places quantity
  51 #endif
  52