Repeatable subtract vs. subtraction of union

[eevleevs]

Hello, I noticed that subtract(a, ...b) is potentially much slower than subtract(a, union(b)) when b has many items.
Why not always perform a union of the items to be subtracted? Are there cases where the operations are not equivalent?

[z3dev]

Hi @eevleevs

Nice observation! We are always looking for ways to improve the performance of the operations. This is definitely going to be investigated.