hledger/Ledger/Amount.hs
2008-10-15 19:54:35 +00:00

111 lines
3.3 KiB
Haskell

{-|
An 'Amount' is some quantity of money, shares, or anything else.
A simple amount is a commodity, quantity pair (where commodity can be anything):
@
$1
£-50
EUR 3.44
GOOG 500
1.5h
90apples
0
@
A mixed amount (not yet implemented) is one or more simple amounts:
@
$50, EUR 3, AAPL 500
16h, $13.55, oranges 6
@
Commodities may be convertible or not. A mixed amount containing only
convertible commodities can be converted to a simple amount. Arithmetic
examples:
@
$1 - $5 = $-4
$1 + EUR 0.76 = $2
EUR0.76 + $1 = EUR 1.52
EUR0.76 - $1 = 0
($5, 2h) + $1 = ($6, 2h)
($50, EUR 3, AAPL 500) + ($13.55, oranges 6) = $67.51, AAPL 500, oranges 6
($50, EUR 3) * $-1 = $-53.96
($50, AAPL 500) * $-1 = error
@
-}
module Ledger.Amount
where
import Ledger.Utils
import Ledger.Types
import Ledger.Commodity
instance Show Amount where show = showAmount
-- | Get the string representation of an amount, based on its commodity's
-- display settings.
showAmount :: Amount -> String
showAmount (Amount (Commodity {symbol=sym,side=side,spaced=spaced,comma=comma,precision=p}) q)
| side==L = printf "%s%s%s" sym space quantity
| side==R = printf "%s%s%s" quantity space sym
where
space = if spaced then " " else ""
quantity = commad $ printf ("%."++show p++"f") q
commad = if comma then punctuatethousands else id
-- | Add thousands-separating commas to a decimal number string
punctuatethousands :: String -> String
punctuatethousands s =
sign ++ (addcommas int) ++ frac
where
(sign,num) = break isDigit s
(int,frac) = break (=='.') num
addcommas = reverse . concat . intersperse "," . triples . reverse
triples [] = []
triples l = [take 3 l] ++ (triples $ drop 3 l)
-- | Get the string representation of an amount, rounded, or showing just "0" if it's zero.
showAmountOrZero :: Amount -> String
showAmountOrZero a
| isZeroAmount a = "0"
| otherwise = showAmount a
-- | is this amount zero, when displayed with its given precision ?
isZeroAmount :: Amount -> Bool
isZeroAmount a@(Amount c _ ) = nonzerodigits == ""
where nonzerodigits = filter (`elem` "123456789") $ showAmount a
instance Num Amount where
abs (Amount c q) = Amount c (abs q)
signum (Amount c q) = Amount c (signum q)
fromInteger i = Amount (comm "") (fromInteger i)
(+) = amountop (+)
(-) = amountop (-)
(*) = amountop (*)
-- | Apply a binary arithmetic operator to two amounts, converting to the
-- second one's commodity and adopting the lowest precision. (Using the
-- second commodity means that folds (like sum [Amount]) will preserve the
-- commodity.)
amountop :: (Double -> Double -> Double) -> Amount -> Amount -> Amount
amountop op a@(Amount ac aq) b@(Amount bc bq) =
Amount bc ((quantity $ convertAmountTo bc a) `op` bq)
-- | Convert an amount to the specified commodity using the appropriate
-- exchange rate.
convertAmountTo :: Commodity -> Amount -> Amount
convertAmountTo c2 (Amount c1 q) = Amount c2 (q * conversionRate c1 c2)
-- | Sum a list of amounts. This is still needed because a final zero
-- amount will discard the sum's commodity.
sumAmounts :: [Amount] -> Amount
sumAmounts = sum . filter (not . isZeroAmount)
nullamt = Amount (comm "") 0
-- temporary value for partial entries
autoamt = Amount (Commodity {symbol="AUTO",side=L,spaced=False,comma=False,precision=0,rate=1}) 0