+/**
+ * <font color=green>an element which matches some set of one-token-long input strings</font>.
+ *
+ * This class is a topology over itself so that Atoms can be
+ * intersected and unioned with each other to result in other
+ * Atom<T>'s (rather than raw Topology<T>'s, which are not Elements).
+ * If you want the latter, use the getTokenTopology() method.
+ */