How can I define a custom equality operation that will be used by immutable Set comparison methods

Question

I have an immutable Set of a class, Set[MyClass], and I want to use the Set methods intersect and diff, but I want them to test for equality using my custom equals method, r

Answer 1

This answer shows a custom mutable Set with user-defined Equality. It could be made immutable by replacing the internal store with a Vector and returning a modified copy of itself upon each operation