> {
+/**
+ * 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> {
- public abstract Topology underlying();
- public abstract String toString();
- public StringBuffer toString(StringBuffer sb) { sb.append(this); return sb; }
+ /** the set (topology) of tokens that can match this element */
+ public abstract Topology getTokenTopology();
+
+ StringBuffer toString(StringBuffer sb) { sb.append(this); return sb; }
}
+