-- prop1 & 2 & 3 & 4, but not prop5
dodgySort4 [] = []
dodgySort4 [x] = [x]
dodgySort4 (x:xs) = sortedList
  where
    list :: [Int]
    replacedList :: [Int]
    sortedList :: [Int]
    list = insertionSort (x:xs)
    replacedList = replaceDups list
    sortedList = insertionSort replacedList


-- replace duplicates with a random number
replaceDups :: [Int] -> [Int]
replaceDups [] = []
replaceDups [x] = [x]
replaceDups (x1:x2:xs)
  | x1 == x2 = replaceDups ([x1] ++ [500] ++ xs)
  | otherwise = x1 : replaceDups (x2:xs)