46 lines
1.5 KiB
Haskell
46 lines
1.5 KiB
Haskell
{-|
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A 'Commodity' is a symbol representing a currency or some other kind of
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thing we are tracking, and some settings that tell how to display amounts
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of the commodity. For the moment, commodities also include a hard-coded
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conversion rate relative to the dollar.
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-}
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module Ledger.Commodity
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where
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import qualified Data.Map as Map
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import Ledger.Utils
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import Ledger.Types
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commoditytests = TestList [
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]
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-- for nullamt, autoamt, etc.
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unknown = Commodity {symbol="",side=L,spaced=False,comma=False,precision=0,rate=1}
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-- convenient amount and commodity constructors, for tests etc.
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dollar = Commodity {symbol="$",side=L,spaced=False,comma=False,precision=2,rate=1}
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euro = Commodity {symbol="EUR",side=L,spaced=False,comma=False,precision=2,rate=0.760383}
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pound = Commodity {symbol="£",side=L,spaced=False,comma=False,precision=2,rate=0.512527}
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hour = Commodity {symbol="h",side=R,spaced=False,comma=False,precision=1,rate=100}
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dollars = Amount dollar
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euros = Amount euro
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pounds = Amount pound
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hours = Amount hour
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defaultcommodities = [dollar, euro, pound, hour, unknown]
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defaultcommoditiesmap :: Map.Map String Commodity
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defaultcommoditiesmap = Map.fromList [(symbol c :: String, c :: Commodity) | c <- defaultcommodities]
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comm :: String -> Commodity
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comm symbol = Map.findWithDefault (error "commodity lookup failed") symbol defaultcommoditiesmap
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-- | Find the conversion rate between two commodities.
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conversionRate :: Commodity -> Commodity -> Double
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conversionRate oldc newc = (rate newc) / (rate oldc)
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