There was a typo in my last email. The input list is [1,4,5,3,3,4] not [1,4,5,3]. - Greg ----- Original Message ---- From: Alexteslin <alexteslin@yahoo.co.uk> To: haskell-cafe@haskell.org Sent: Tuesday, July 10, 2007 1:40:56 PM Subject: [Haskell-cafe] function unique 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. -- View this message in context: http://www.nabble.com/function-unique-tf4058328.html#a11528933 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ____________________________________________________________________________________ It's here! Your new message! Get new email alerts with the free Yahoo! Toolbar. http://tools.search.yahoo.com/toolbar/features/mail/