> {
+/**
+ * an element which matches some set of one-token-long input strings.
+ *
+ *
+ * This class is a topology over itself (yes, that's sort of Frege'd up) so that
+ * Atoms can be intersected and unioned with each other to result in
+ * other Atom's (rather than raw Topology's, which are
+ * not Elements). If you want the latter, use the getTokenTopology()
+ * method.
+ *
+ */
+public abstract class Atom extends Element implements Topology> {
+
+ /** the set (topology) of tokens that can match this element */
+ public abstract Topology getTokenTopology();
- public abstract Topology underlying();
- public abstract String toString();
- public StringBuffer toString(StringBuffer sb) { sb.append(this); return sb; }
+ StringBuffer toString(StringBuffer sb) { sb.append(this); return sb; }
}
+