Haskell - get items that occur only once

Question

Im trying to figure out how to create a new list that has only the elements that occur only once. I can't use recursion either.

This is a small part of a bigger function. Im trying to write a function to get the Intersect of two sets. Basically i combined the sets. Then sorted. Then i want to combine that with set B and get rid of all the duplicates in that set. Unless someone else knows an easier way.

I can use high order functions, but i can't use recursion.

Thanks

Edit: Example:

[1,2,3,3,4,4,5,5] Should come out as [1,2]

Answer 1

I hope this hint is sufficiently vague. :)

Think about grouping duplicate elements together.

Answer 2

Think about what data structure you'd use to keep track of how many times each thing shows up.

Answer 3

This question was already asked before and essentially you just want to group them together by counting the number of elements and then only extracting those with a count of one. (probably using 'filter')

Please see http://stackoverflow.com/questions/3710976/counting-unique-elements-in-a-list/3713886#3713886

Answer 4

How about:

concat $ filter (null . tail) $ group [1,2,3,3,4,4,5,5]