WARNING: pending event for node `$1'; ignoring request.
The above message is displayed whenever the user tries to set a node to a value, when it is already scheduled to take on a different value in the event-queue. This is a safe-guard to prevent users from accidentally modifying events that are caused by the circuits. This message also appears if a user tries to set a node to different values without cycle-ing in between. To forcefully override the event queue, use the setf command, which will issue the following warning.
WARNING: pending event for node `$1' was overidden.
Assertion failures are pretty self-documenting.