SET-TO-LIST
===========

syntax: (set-to-list <evaluates-to <set-of A (...)>>
                     [:EXTRACT-FN
                        <lisp-type: function>])

        ==> List with the extracted elements

This function extracts elements from the set with
the extraction function.

example: >(list-to-set '(2 "house" 3 4 "window" 5))
         #<set-of T (...)>
      
         >(set-to-list * :EXTRACT-FN #'stringp)
         ("house" "window")