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module Election(
Election,
createElection,
doCount
) where
import qualified System.IO as IO
import qualified Control.Monad as Con
import qualified Control.Monad.Trans.Either as ET
import qualified Control.Monad.IO.Class as MIO
import qualified Data.List as List
import qualified Data.Either.Unwrap as Either
import qualified Counter as Sen
import qualified Candidate as Typ
import qualified CSV as CSV
data Election = Election
{ getEntries :: [Entry]
, getCounter :: Sen.SenateCounter
, getLogDir :: FilePath
, getTotalPapers :: Int
, getQuota :: Int
, getNextLogNum :: Int
, getVacancies :: Int
, isDone :: Bool }
data Entry = Entry
{ getID :: Typ.CandidateID
, getVoteChange :: Int
, getTotalVotes :: Int
, getCritTrace :: [Trace]
, getStatus :: Status
, getChanged :: Bool }
deriving (Eq)
data Trace = Trace
{ getCriteria :: Sen.Criteria
, getTransferVal :: Float }
deriving (Eq)
data Status = Running | Elected | Eliminated
deriving (Show, Eq)
createElection :: FilePath -> Sen.SenateCounter -> Int -> IO Election
createElection outDir counter numToElect = do
entries <- mapM (candToEntry counter) (Sen.getBallot counter)
let total = Sen.getTotal counter
quota = 1 + floor ((fromIntegral total) / (fromIntegral (numToElect + 1)))
return (Election entries counter outDir total quota 1 numToElect False)
candToEntry :: Sen.SenateCounter -> Typ.CandidateID -> IO Entry
candToEntry counter candidate = do
let criteria = [(1,candidate)]
trace = Trace criteria 1
firstPrefs <- Sen.doCount counter criteria
return (Entry candidate firstPrefs firstPrefs [trace] Running False)
doCount :: Election -> IO ()
doCount e = do
e' <- writeLog e
-- these following calculations probably aren't the
-- intended use of Either monads, but the pattern fits
-- and it's certainly a lot better than a bunch of
-- if-them-else constructs in haskell
r <- ET.eitherT return return $
checkDone e' >>=
electSomeone >>=
checkNoQuota >>=
excludeSomeone
Con.when (not (isDone r)) $ doCount r
checkDone :: Election -> ET.EitherT Election IO Election
checkDone e = do
let running = filter ((== Running) . getStatus) (getEntries e)
if (getVacancies e == 0 || length running == 0)
then ET.left (e { isDone = True })
else ET.right e
partBeforeAfter :: (Eq a) => a -> [a] -> ([a],[a])
partBeforeAfter item list =
let (x,y) = List.break (== item) list
in if (length y <= 1)
then (x,[])
else (x,tail y)
electSomeone :: Election -> ET.EitherT Election IO Election
electSomeone e = do
let (running, notRunning) = List.partition ((== Running) . getStatus) (getEntries e)
electedEntry = List.maximumBy (\x y -> compare (getTotalVotes x) (getTotalVotes y)) running
(beforeEntries, afterEntries) = partBeforeAfter electedEntry (getEntries e)
newTransferValue = (fromIntegral (getTotalVotes electedEntry - getQuota e)) /
(fromIntegral (getTotalVotes electedEntry))
revisedElectedEntry = electedEntry
{ getStatus = Elected
, getChanged = True
, getTotalVotes = (getQuota e)
, getVoteChange = (getQuota e) - (getTotalVotes electedEntry) }
if (getTotalVotes electedEntry >= getQuota e)
then do
revisedBeforeEntries <- MIO.liftIO $ transferVotes (getCounter e) newTransferValue electedEntry beforeEntries
revisedAfterEntries <- MIO.liftIO $ transferVotes (getCounter e) newTransferValue electedEntry afterEntries
let revisedEntries = revisedBeforeEntries ++ [revisedElectedEntry] ++ revisedAfterEntries
ET.left (e { getEntries = revisedEntries, getVacancies = (getVacancies e) - 1 })
else ET.right e
excludeSomeone :: Election -> ET.EitherT Election IO Election
excludeSomeone e = do
let (running, notRunning) = List.partition ((== Running) . getStatus) (getEntries e)
excludedEntry = List.minimumBy (\x y -> compare (getTotalVotes x) (getTotalVotes y)) running
(beforeEntries, afterEntries) = partBeforeAfter excludedEntry (getEntries e)
revisedExcludedEntry = excludedEntry
{ getStatus = Eliminated
, getChanged = True
, getTotalVotes = 0
, getVoteChange = -(getTotalVotes excludedEntry) }
if (getTotalVotes excludedEntry < getQuota e)
then do
revisedBeforeEntries <- MIO.liftIO $ transferVotes (getCounter e) 1 excludedEntry beforeEntries
revisedAfterEntries <- MIO.liftIO $ transferVotes (getCounter e) 1 excludedEntry afterEntries
let revisedEntries = revisedBeforeEntries ++ [revisedExcludedEntry] ++ revisedAfterEntries
ET.left (e { getEntries = revisedEntries })
else ET.right e
transferVotes :: Sen.SenateCounter -> Float -> Entry -> [Entry] -> IO [Entry]
transferVotes counter value from to = do
let addToCriteria candID crit =
let maxRank = fst (List.maximumBy (\x y -> compare (fst x) (fst y)) crit)
in (maxRank + 1, candID):crit
addToTrace candID trace = trace
{ getCriteria = addToCriteria candID (getCriteria trace)
, getTransferVal = value * (getTransferVal trace) }
transferFunc entryFrom entryTo = do
let newTraces = map (addToTrace (getID entryTo)) (getCritTrace entryFrom)
voteList <- Con.mapM (Sen.doCount counter) (map getCriteria newTraces)
let changeList = zipWith (*) (map getTransferVal newTraces) (map fromIntegral voteList)
totalVoteChange = List.foldl' (+) 0 (map floor changeList)
return (entryTo
{ getVoteChange = totalVoteChange
, getTotalVotes = (getTotalVotes entryTo) + totalVoteChange
, getCritTrace = newTraces
, getChanged = True })
Con.mapM (transferFunc from) to
checkNoQuota :: Election -> ET.EitherT Election IO Election
checkNoQuota e = do
let (running, notRunning) = List.partition ((== Running) . getStatus) (getEntries e)
electedEntry = List.maximumBy (\x y -> compare (getTotalVotes x) (getTotalVotes y)) running
(beforeEntries, afterEntries) = partBeforeAfter electedEntry (getEntries e)
revisedElectedEntry = electedEntry
{ getStatus = Elected
, getChanged = True
, getVoteChange = 0 }
revisedBeforeEntries = map (\x -> x { getVoteChange = 0, getChanged = False }) beforeEntries
revisedAfterEntries = map (\x -> x { getVoteChange = 0, getChanged = False }) afterEntries
revisedEntries = revisedBeforeEntries ++ [revisedElectedEntry] ++ revisedAfterEntries
if (length running <= getVacancies e + 1)
then ET.left (e { getEntries = revisedEntries, getVacancies = getVacancies e - 1 })
else ET.right e
writeLog :: Election -> IO Election
writeLog e = do
let logName = (getLogDir e) ++ "/" ++ (show (getNextLogNum e)) ++ ".csv"
header = ["Vacancies", "Total Papers", "Quota", "Candidate", "Votes", "Transfer", "Status", "Changed"]
static = [show (getVacancies e), show (getTotalPapers e), show (getQuota e)]
dynFunc c = [getID c, show (getTotalVotes c), show (getVoteChange c), show (getStatus c), show (getChanged c)]
records = map (\x -> static ++ dynFunc x) (getEntries e)
headerLine = CSV.unParseRecord CSV.defaultSettings header
recordLines = map (CSV.unParseRecord CSV.defaultSettings) records
output = unlines (headerLine:recordLines)
IO.writeFile logName output
return (e { getNextLogNum = 1 + getNextLogNum e })
|
