Еще одна задача из раздела "Fortran"

sign :: Int -> Int   -- не нашел стандартной функции...
sign n | (n == 0) = 0
       | (n <  0) = -1
       | otherwise = 1
       
maxSeq :: [Int] -> [Int] -> [Int] -> [Int]
maxSeq [] c r = if ((length c) > (length r)) then c else r
maxSeq (x:xs) [] r = maxSeq xs [x] r 
maxSeq (x:xs) inic@(c:cs) r | ((sign x) == (sign c)) = maxSeq xs (inic ++ [x]) r
                            | otherwise = if ((length inic) > (length r)) then
                                             maxSeq xs [x] inic
                                          else
                                             maxSeq xs [x] r

subSeq [] = []
subSeq l@(h:t) = take q (drop sp l)
    where
        (sp,q) = loop t (signum h) 1 0 1 (0,1)
        loop [] _ _ pos q a@(p',q') = if q' >= q then a else (pos,q)
        loop (h:t) zn curPos pos q ac
            | signum h == zn = loop t zn (curPos+1) pos (q+1) ac
            | otherwise = loop t (-zn) (curPos+1) curPos 1 newAcc
            where newAcc = if snd ac >= q then ac else (pos,q)

import Data.List (groupBy, maximumBy)
import Data.Function (on)
import Data.Ord (comparing)
import Control.Arrow ((&&&))
 
groupBySign :: (Num a, Eq a) => [a] -> [[a]]
groupBySign = groupBy ((==) `on` signum)
 
maxSequenceByLength :: [[a]] -> [a]
maxSequenceByLength = fst . maximumBy (comparing snd) . map (id &&& length)
 
maxSubsequenceOfSameSign :: (Num a, Eq a) => [a] -> [a]
maxSubsequenceOfSameSign = maxSequenceByLength . groupBySign

sameSign = on (==) signum
length' = on compare length
maxSeq = maximumBy length' . groupBy sameSign