hailstone x 
 | even x = div x 2 
 | odd x = 3*x + 1 


hailLen x 
 | x> 1 = print hail n x 
 | x == 1 = 1 

  where hail n 1 = n 
        hail n x = hail (n+1) (hailstone x) 
        n = 0 



--divisors :: Int -> [Int] 
divisors n = [ i | i <- [2..(n `div` 2)] , n `mod` i == 0] 


join c []= " "
join c (x:xs) 
  | c== "X"  = x
  | otherwise = x ++ rest 
      where rest = c ++ join c xs

pythagorean x = [(a,b,c)|a<-[1..x], b<-[1..a], c<-[1..x], (a^2)+(b^2) == (c^2)]