IS-UNDETERMINED-SET =================== syntax: (is-undetermined-set <evaluates-to set>) ==> T | NIL This function checks, whether the given set is an indefinite empty set. Warning: length works on vectors AND lists! example: >(difference-of-set *capital-cities* *cities*) #<set-of T ()> >(is-undetermined-set *) NIL >(is-undetermined-set (ask-instance-values 'landscape Paris)) T ; i.e. the set is indefinite and empty!