// NOTE: sets are immutable
val set_numbers: Set[Int] = Set(1, 3, 5, 7, 9) // Set(5, 1, 9, 7, 3)
set_numbers.contains(3) // true
set_numbers.contains(2) // false
// mutable set
val set_mutable_one = scala.collection.mutable.Set(1, 3, 5)
val set_mutable_two = scala.collection.mutable.Set(5, 7, 9)
set_mutable_two += 11 // Set(9, 5, 7, 11)
set_mutable_two -= 11 // Set(9, 5, 7)
// set operations
val A = set_mutable_one.clone
val B = set_mutable_two.clone
A | B // Set(9, 1, 5, 3, 7)
A & B // Set(5)
A &~ B // Set(1, 3)
A union B // Set(9, 1, 5, 3, 7)
A intersect B // Set(5)
A diff B // Set(1, 3)
A subsetOf B // false