lib/Hcompta/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.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 zero :: Quantity
  28 is_zero :: Quantity -> Bool
  29 round :: Word8 -> Quantity -> Quantity
  30 #ifdef DOUBLE
  31 representation = "Double"
  32 zero = 0.0
  33
  34 round n f = fromInteger $ round $ (f * (10^n)) / (10.0^^n)
  35
  36 is_zero = (== 0) . decimalMantissa
  37 --is_zero decimal_places quantity =
  38 --      floor quantity == 0 && -- NOTE: check integral part, in case of an overflow in roundTo'
  39 --      0 == roundTo' decimal_places quantity
  40 --      where
  41 --              roundTo' n f = fromInteger $ round $ f * (10 ^ n)
  42
  43 #else
  44 representation = "Decimal"
  45 zero = fromInteger 0
  46
  47 round = Data.Decimal.roundTo
  48
  49 is_zero = (== 0) . decimalMantissa
  50 --is_zero decimal_places quantity =
  51 --      (== 0) $ decimalMantissa $
  52 --      Hcompta.Amount.Quantity.round decimal_places quantity
  53 #endif
  54