Syntax
(defmessage-handler USER delete primary ())
This handler is responsible for deleting an instance from the system. The user must directly send a delete message to an instance. User-defined delete message-handlers should not prevent the system message-handler from responding to a delete message (see section 9.5.3). The handler returns the symbol TRUE if the instance was successfully deleted, otherwise it returns the symbol FALSE.
Example
CLIPS> (send [Rolls-Royce] delete)
MSG >> delete ED:1 (<Instance-Rolls-Royce>)
HND >> delete primary in class USER
ED:1 (<Instance-Rolls-Royce>)
HND << delete primary in class USER
ED:1 (<Stale Instance-Rolls-Royce>)
MSG << delete ED:1 (<Stale Instance-Rolls-Royce>)
TRUE
CLIPS>