Note also that this mechanism is usually hidden behind a macro. In user code one would just write: (with-progress-noted (datum data) (process-partial

Note also that this mechanism is usually hidden behind a macro. In user code one would just write: (with-progress-noted (datum data) (process-partial-data datum)) And this then would expand into a machinery like above. The Lisp Machine OS had a system-wide progress bar at the bottom of the screen, which then would show the progress of some process - usually the front process or something related.