scala> :paste
// Entering paste mode (ctrl-D to finish)

implicit class IteratorWrapper[T](it: Iterator[T]) {
    def distinct = new Iterator[T] {
        def hasNext = it.hasNext

        var seen = Set.empty[T]
        def next = {
            val v = it.next
            if (!seen(v)) {
                seen += v
                v
            } else next
        }
    }
}

// Exiting paste mode, now interpreting.

defined class IteratorWrapper

scala> val a = Iterator(1,1)
a: Iterator[Int] = non-empty iterator

scala> a.next
res0: Int = 1

scala> a.hasNext
res1: Boolean = true

scala> a.next
res2: Int = 1