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