My gripe with Swift (and I've written a lot of it) for purposes requiring a lot of number crunching is the performance issues associated with default use of cop

My gripe with Swift (and I've written a lot of it) for purposes requiring a lot of number crunching is the performance issues associated with default use of copy-on-write types/ease of accidentally writing O(N^2) code. In Objective C the behavior was more obvious with NSMutable* types being front and center.