>And in most circumstances it suffices to stop and restart. Only if your program is small and/or does trivial stuff. In ordinary languages, there's a signific

>And in most circumstances it suffices to stop and restart. Only if your program is small and/or does trivial stuff. In ordinary languages, there's a significant loss of time to achieve the following, once a bug is found: - stop the running program - correct the offending function - recompile the program - restart the program again - interact with the program until you achieve the same conditions that caused the bug - confirm that the bug doesn't happen again. On a lisp system the steps are: - correct the offending function - re-compile the function (this takes milliseconds); this can even be done while other threads are running. - restart the stack frame where the error condition was found, and immediately confirm that the error doesn't happen again. The difference in productivity is remarkable.