No quite. By 'random access array' I meant changing an arbitrary array element, anywhere in memory. Suppose you have array mutation, but the changes are only l

No quite. By 'random access array' I meant changing an arbitrary array element, anywhere in memory. Suppose you have array mutation, but the changes are only local. Then as TuringTest pointed out, there are efficient ways to make those local changes in a functional programming language without the log(N) overhead.