Is there any data structure in Appian similar to a HashSet? I would l

If you have an array, you an call the union function to remove the duplicates:
union(pv!array,pv!array)
forum.appian.com/.../Set_Functions

Hope that helps!

I know about Union, this will eliminate duplicates. But I would like to detect the eliminated duplicate? I was thinking of a loop and using the contains function. If the array contains the element already, it will not add it and that would be detected as duplicate element?

Instead of a loop, try using a looping function with contains.
forum.appian.com/.../Looping_Functions
Hope that helps!

The intersection function also gives you the duplicates.

You can use distinct() function to remove duplicates,but this function not appears in Functions list,even though you can use it