- box-swap! BOX FUNC #!optional OBJECT...procedure
Changes the boxed value of BOX to (FUNC <BOX-VALUE> OBJECT...). Will signal an exception for an immutable BOX}. Returns the new value of {{BOX.
Changes the boxed value of BOX to (FUNC <BOX-VALUE> OBJECT...). Will signal an exception for an immutable BOX}. Returns the new value of {{BOX.