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.Bool
   9 import           Data.Data
  10 #ifdef DOUBLE
  11 #else
  12 import           Data.Decimal
  13 #endif
  14 import           Data.Eq (Eq(..))
  15 import           Data.String (String)
  16 import           Data.Word
  17 import           Data.Typeable ()
  18 import           Prelude ((.))
  19
  20 #ifdef DOUBLE
  21 type Quantity
  22  = Double
  23 #else
  24 type Quantity
  25  = Decimal
  26 deriving instance Data Quantity
  27 #endif
  28
  29 representation :: String
  30 zero :: Quantity
  31 is_zero :: Quantity -> Bool
  32 round :: Word8 -> Quantity -> Quantity
  33 #ifdef DOUBLE
  34 representation = "Double"
  35 zero = 0.0
  36
  37 round n f = fromInteger $ round $ (f * (10^n)) / (10.0^^n)
  38
  39 is_zero = (== 0) . decimalMantissa
  40 --is_zero decimal_places quantity =
  41 --      floor quantity == 0 && -- NOTE: check integral part, in case of an overflow in roundTo'
  42 --      0 == roundTo' decimal_places quantity
  43 --      where
  44 --              roundTo' n f = fromInteger $ round $ f * (10 ^ n)
  45
  46 #else
  47 representation = "Decimal"
  48 zero = 0
  49
  50 round = Data.Decimal.roundTo
  51
  52 is_zero = (== 0) . decimalMantissa
  53 --is_zero decimal_places quantity =
  54 --      (== 0) $ decimalMantissa $
  55 --      Hcompta.Amount.Quantity.round decimal_places quantity
  56 #endif
  57