hledger/Currency.hs

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module Currency
where
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import qualified Data.Map as Map
import Data.Map ((!))
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import Utils
import Types
currencies =
[
Currency "$" 1
,Currency "EUR" 0.760383
,Currency "£" 0.512527
,Currency "h" 60 -- hours
,Currency "m" 1 -- minutes
]
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currencymap = Map.fromList [(sym, c) | c@(Currency sym rate) <- currencies]
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getcurrency :: String -> Currency
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getcurrency s = Map.findWithDefault (Currency s 1) s currencymap
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conversionRate :: Currency -> Currency -> Double
conversionRate oldc newc = (rate newc) / (rate oldc)
-- convenient amount constructors
dollars n = Amount (getcurrency "$") n 2
euro n = Amount (getcurrency "EUR") n 2
pounds n = Amount (getcurrency "£") n 2
hours n = Amount (getcurrency "h") n 2
minutes n = Amount (getcurrency "m") n 2
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