lib/Hcompta/Amount/Quantity.hs

   1 {-# LANGUAGE CPP #-}
   2 {-# LANGUAGE DeriveDataTypeable #-}
   3 {-# LANGUAGE FlexibleInstances #-}
   4 {-# LANGUAGE StandaloneDeriving #-}
   5 {-# OPTIONS_GHC -fno-warn-orphans #-}
   6 module Hcompta.Amount.Quantity where
   7
   8 import Data.Data
   9 #ifdef DOUBLE
  10 #else
  11 import Data.Decimal
  12 #endif
  13 import Data.Word
  14 import Data.Typeable ()
  15
  16 #ifdef DOUBLE
  17 type Quantity
  18  = Double
  19 #else
  20 type Quantity
  21  = Decimal
  22 deriving instance Data Quantity
  23 #endif
  24
  25 representation :: String
  26 zero :: Quantity
  27 is_zero :: Quantity -> Bool
  28 round :: Word8 -> Quantity -> Quantity
  29 #ifdef DOUBLE
  30 representation = "Double"
  31 zero = 0.0
  32
  33 round n f = fromInteger $ round $ (f * (10^n)) / (10.0^^n)
  34
  35 is_zero = (== 0) . decimalMantissa
  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 zero = 0
  45
  46 round = Data.Decimal.roundTo
  47
  48 is_zero = (== 0) . decimalMantissa
  49 --is_zero decimal_places quantity =
  50 --      (== 0) $ decimalMantissa $
  51 --      Hcompta.Amount.Quantity.round decimal_places quantity
  52 #endif
  53