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81 lines
1.9 KiB
Haskell
81 lines
1.9 KiB
Haskell
module BasicTypes
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where
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import Utils
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type Date = String
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type DateTime = String
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-- amounts
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{- a simple amount is a currency, quantity pair:
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0
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$1
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£-50
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EUR 3.44
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HRS 1.5
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DAYS 3
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GOOG 500
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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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HRS 16, $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, HRS 2) + $1 = ($6, HRS 2)
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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) * $-1 = error
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-}
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type Currency = String
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data Amount = Amount {
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currency :: Currency,
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quantity :: Double
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} deriving (Eq,Ord)
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instance Show Amount where show = showAmountRoundedOrZero
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nullamt = Amount "" 0
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showAmountRoundedOrZero :: Amount -> String
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showAmountRoundedOrZero (Amount cur qty) =
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let rounded = printf "%.2f" qty in
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case rounded of
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"0.00" -> "0"
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"-0.00" -> "0"
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otherwise -> cur ++ rounded
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instance Num Amount where
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abs (Amount c q) = Amount c (abs q)
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signum (Amount c q) = Amount c (signum q)
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fromInteger i = Amount "$" (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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conversionRate :: Currency -> Currency -> Double
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conversionRate oldc newc = (rate newc) / (rate oldc)
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rate :: Currency -> Double
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rate "$" = 1.0
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rate "EUR" = 0.760383
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rate "£" = 0.512527
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rate _ = 1
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data MixedAmount = MixedAmount [Amount] deriving (Eq,Ord)
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