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115 lines
2.6 KiB
Haskell
115 lines
2.6 KiB
Haskell
module Amount
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where
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import Utils
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import BasicTypes
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{-
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a simple amount is a currency, quantity pair:
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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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90m
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0
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a mixed amount is one or more simple amounts:
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$50, EUR 3, AAPL 500
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16h, $13.55, oranges 6
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arithmetic:
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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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tests = runTestTT $ test [
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show (dollars 1) ~?= "$1.00"
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,
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show (hours 1) ~?= "1h" -- currently h1.00
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,
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parseAmount "$1" ~?= dollars 1 -- currently 0
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]
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-- currency
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data Currency = Currency {
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symbol :: String,
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rate :: Double -- relative to the dollar
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} deriving (Eq,Show)
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currencies =
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[
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Currency "$" 1
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,Currency "EUR" 0.760383
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,Currency "£" 0.512527
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,Currency "h" 60 -- hours
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,Currency "m" 1 -- minutes
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]
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getcurrency :: String -> Currency
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getcurrency s = head $ [(Currency symbol rate) | (Currency symbol rate) <- currencies, symbol==s]
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-- convenience
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dollars = Amount $ getcurrency "$"
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euro = Amount $ getcurrency "EUR"
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pounds = Amount $ getcurrency "£"
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hours = Amount $ getcurrency "h"
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minutes = Amount $ getcurrency "m"
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conversionRate :: Currency -> Currency -> Double
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conversionRate oldc newc = (rate newc) / (rate oldc)
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-- amount
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data Amount = Amount {
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currency :: Currency,
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quantity :: Double
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} deriving (Eq)
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instance Show Amount where show = showAmountRoundedOrZero
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nullamt = dollars 0
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parseAmount :: String -> Amount
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parseAmount s = nullamt
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showAmountRoundedOrZero :: Amount -> String
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showAmountRoundedOrZero (Amount cur qty) =
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let rounded = printf "%.2f" qty in
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case rounded of
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"0.00" -> "0"
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"-0.00" -> "0"
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otherwise -> (symbol cur) ++ rounded
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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 (getcurrency "$") (fromInteger i)
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(+) = amountAdd
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(-) = amountSub
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(*) = amountMul
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Amount ac aq `amountAdd` b = Amount ac (aq + (quantity $ toCurrency ac b))
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Amount ac aq `amountSub` b = Amount ac (aq - (quantity $ toCurrency ac b))
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Amount ac aq `amountMul` b = Amount ac (aq * (quantity $ toCurrency ac b))
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toCurrency :: Currency -> Amount -> Amount
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toCurrency newc (Amount oldc q) =
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Amount newc (q * (conversionRate oldc newc))
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-- mixed amounts
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--data MixedAmount = MixedAmount [Amount] deriving (Eq,Ord)
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