splitTwos

splits.hs

flipT :: (x,y) -> (y,x)
flipT (x,y) = (y,x)

splitOnes :: (Eq a, Ord a) => [a] -> [([a],[a])]
splitOnes xs = map flipT . M.toList . M.fromList . map flipT . map (\n -> partition (==n) xs) $ xs

splitTwos :: (Eq a, Ord a) => [a] -> [([a],[a])]
splitTwos xs = map flipT . M.toList . M.fromList . concatMap splitAgain . splitOnes $ xs
    where
        splitAgain (n,xs) = 
            let morePairings = splitOnes xs
            in  map (\(n',rxs) -> (rxs, n++n')) $ morePairings