39 lines
1012 B
Haskell
39 lines
1012 B
Haskell
{-|
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A 'Currency' is a symbol and a conversion rate relative to the
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dollar. Currency symbols are parsed from the ledger file, rates are
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currently hard-coded.
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-}
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module Ledger.Currency
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where
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import qualified Data.Map as Map
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import Data.Map ((!))
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import Ledger.Utils
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import Ledger.Types
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currencies =
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[
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Currency "$" 1
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,Currency "EUR" 0.760383
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,Currency "£" 0.512527
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,Currency "h" 60 -- hours
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,Currency "m" 1 -- minutes
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]
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currencymap = Map.fromList [(sym, c) | c@(Currency sym rate) <- currencies]
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getcurrency :: String -> Currency
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getcurrency s = Map.findWithDefault (Currency s 1) s currencymap
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conversionRate :: Currency -> Currency -> Double
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conversionRate oldc newc = (rate newc) / (rate oldc)
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-- | convenient amount constructors
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dollars n = Amount (getcurrency "$") n 2
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euro n = Amount (getcurrency "EUR") n 2
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pounds n = Amount (getcurrency "£") n 2
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hours n = Amount (getcurrency "h") n 2
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minutes n = Amount (getcurrency "m") n 2
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