[Haskell-cafe] function unique

[Alexteslin]

Hi, i am a beginner to Haskell and i have a beginner's question to ask.

An exercise asks to define function unique :: [Int] -> [Int], which outputs
a list with only elements that are unique to the input list (that appears no
more than once).  I defined a function with list comprehension which works
but trying to implement with pattern matching and primitive recursion with
lists and doesn't work.

unique :: [Int] -> [Int]
unique xs = [x | x <- xs, elemNum2 x xs == 1]


elemNum2 :: Int -> [Int] -> Int
elemNum2 el xs = length [x| x <- xs, x == el]

//This doesn't work, I know because the list shrinks and produces wrong
result but can not get a right //thinking

unique2 :: [Int] -> [Int]
unique2 [] = []
unique2 (x:xs)
	|elemNum2 x xs == 1 = x:unique2 xs
	|otherwise = unique2 xs


Any help to a right direction would be very appreciated, thanks.
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