90 lines
1.8 KiB
Haskell
90 lines
1.8 KiB
Haskell
import Data.List (groupBy, sortBy, intercalate)
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type Item = (Int, String)
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type ItemList = [Item]
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type ItemGroups = [ItemList]
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type RankItem a = (a, Int, String)
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type RankItemList a = [RankItem a]
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-- make sure the input is ordered and grouped by score
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prepare :: ItemList -> ItemGroups
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prepare = groupBy gf . sortBy (flip compare)
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where
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gf (a, _) (b, _) = a == b
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-- give an item a rank
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rank
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:: Num a
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=> a -> Item -> RankItem a
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rank n (a, b) = (n, a, b)
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-- ranking methods
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standard, modified, dense, ordinal :: ItemGroups -> RankItemList Int
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standard = ms 1
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where
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ms _ [] = []
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ms n (x:xs) = (rank n <$> x) ++ ms (n + length x) xs
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modified = md 1
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where
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md _ [] = []
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md n (x:xs) =
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let l = length x
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nl = n + l
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nl1 = nl - 1
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in (rank nl1 <$> x) ++ md (n + l) xs
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dense = md 1
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where
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md _ [] = []
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md n (x:xs) = map (rank n) x ++ md (n + 1) xs
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ordinal = zipWith rank [1 ..] . concat
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fractional :: ItemGroups -> RankItemList Double
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fractional = mf 1.0
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where
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mf _ [] = []
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mf n (x:xs) =
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let l = length x
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o = take l [n ..]
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ld = fromIntegral l
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a = sum o / ld
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in map (rank a) x ++ mf (n + ld) xs
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-- sample data
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test :: ItemGroups
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test =
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prepare
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[ (44, "Solomon")
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, (42, "Jason")
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, (42, "Errol")
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, (41, "Garry")
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, (41, "Bernard")
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, (41, "Barry")
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, (39, "Stephen")
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]
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-- print rank items nicely
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nicePrint
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:: Show a
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=> String -> RankItemList a -> IO ()
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nicePrint xs items = do
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putStrLn xs
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mapM_ np items
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putStr "\n"
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where
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np (a, b, c) = putStrLn $ intercalate "\t" [show a, show b, c]
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main :: IO ()
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main = do
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nicePrint "Standard:" $ standard test
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nicePrint "Modified:" $ modified test
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nicePrint "Dense:" $ dense test
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nicePrint "Ordinal:" $ ordinal test
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nicePrint "Fractional:" $ fractional test
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