6.41.3  Union of two sets or of two lists: union

The union operator is an infixed operator that finds the union of the elements of two sets or lists; the result will always be a set.

Examples.

• Input:
  set[1,2,3,4] union set[5,6,3,4]
  or:
  %{1,2,3,4%} union %{5,6,3,4%}
  Output:

  ⟦ 1,2,3,4,5,6 ⟧

• Input:
  [1,2,3] union [2,5,6]
  Output:

  ⟦ 1,2,3,5,6⟧