import Control.SetFunctions
import Data.List ( nub )

-- Permutations with functional patterns
perm :: Data a => [a] -> [a]
perm []                = []
perm (xs ++ [x] ++ ys) = x : perm (xs ++ ys)

-- Are there two adjacent elements out of order?
someDescending :: [Int] -> Bool
--someDescending (_ ++ [x,y] ++ _) | x>y = True
someDescending (_ ++ x : y : _) | x>y = True

-- A sorted list of a given list is a permutation which is not "out of order":
sort :: [Int] -> [Int]
sort xs | isEmpty ((set1 someDescending) p) = p
 where p = perm xs


-------------------------------------------------------------------------

-- ACM programming contest:
-- find the length of a given list until the first repeated element

-- lengthUpToRepeat [1,2,3,42,56,87,2,3,1] --> 7
lengthUpToRepeat :: [Int] -> Int
lengthUpToRepeat (xs ++ [x] ++ _)
  | x `elem` xs && nub xs == xs
  = length xs + 1