zipper x y = (sqrt x + sqrt y, x, y)
 
predicateA (z,_,_) = z > 9 && z < 99
a = filter predicateA [ zipper x y | x <- [1..], y <- [1..] ]
 
predicateBDrop (z,_,_) = z <= 9
predicateBTake (z,_,_) = z < 99
limit = (takeWhile predicateBTake) . (dropWhile predicateBDrop)
calcZ ys x = limit $ map (zipper x) ys
b = concat $ takeWhile (not . null) $ map (calcZ [1..]) [1..]
 
last2 []     = []
last2 [x]    = [x]
last2 [x, y] = [x,y]
last2 (x:xs) = last2 xs
 
run xs = do
	mapM_ print $ take 2 xs
	putStrLn ".."
	mapM_ print $ last2 xs
	putStrLn $ "total items count: " ++ show (length xs)
 
main = run b
 
 

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