Clojurians Log v2

slightly confused about the serial (ordering) rules -> do evals always run in serial per-session but can be parallel between sessions? And operations are not guaranteed to return in-order wrt eachother even in one session, but evals for a single session are guaranteed to return in-order wrt other evals in that same session? And evals not guaranteed to return in order wrt non-evals in the same session?