Functional Programming: Does a list only contain unique items?

Question

I\'m having an unsorted list and want to know, whether all items in it are unique.
My naive approach would be

val l = List(1,2,3,4,3)
def isUniqueList(l: List[Int         


        

Answer 1

A more efficient method would be to attempt to find a dupe; this would return more quickly if one were found:

var dupes : Set[A] = Set.empty

def isDupe(a : A) = if (dupes(a)) true else { dupes += a; false }

//then
l exists isDupe