+(defun clear-system (name)
+ "Clear the entry for a system in the database of systems previously loaded.
+Note that this does NOT in any way cause the code of the system to be unloaded."
+ ;; There is no "unload" operation in Common Lisp, and a general such operation
+ ;; cannot be portably written, considering how much CL relies on side-effects
+ ;; of global data structures.
+ ;; Note that this does a setf gethash instead of a remhash
+ ;; this way there remains a hint in the *defined-systems* table
+ ;; that the system was loaded at some point.
+ (setf (gethash (coerce-name name) *defined-systems*) nil))
+