union - return the union of elements in two arrays
arr1.union(arr2)
The union() method returns a vector containing
all unique elements from both arr1 and
arr2. Duplicate elements are only included once.
This is similar to APL
vec ∪ arr.
A vector containing the unique elements from both input arrays.
ArgCheck if exactly one argument is not
provided.
a = [1, 2, 3]
b = [3, 4, 5]
a.union(b)
[1, 2, 3, 4, 5]