The comparison is "cheap" if you can speculate through it & even then isn't free. If your comparison is 50/50 on branching then you're going to pay a penalty ev

The comparison is "cheap" if you can speculate through it & even then isn't free. If your comparison is 50/50 on branching then you're going to pay a penalty every time you hit that code path. It's entirely possible that the map operation is going to dominate the check, I'm just highlighting it's not free and it's a good idea to validate the cost somehow first (but also recognize there are applications you're going to penalize without them realizing it).