On 11/01/2015 22:15, Arthur A. Gleckler wrote:

The problem with that is that it's O(N), whereas the optional parameter
allows it to be O(1).  Think of accumulating incoming batches of work.
Each batch could be added to the existing queue without copying.

Maybe I'm misunderstanding but it would cost O(N) if the list of given
queue is copied (that's what John suggested) and my imaginary procedure
list-queue-add-back-all! might only cost O(1) if it wouldn't copy the
list (though there is a procedure which mutates queue's elements so it
should take O(N) to copy for safety).