> {
+/**
+ *
+ * an element which matches some set of one-token-long input strings
+ * .
+ *
+ *
+ * This class is a topology over itself (yes, this is impredicative).
+ * This means that you can call Atom.union(Atom) and get back an Atom.
+ * If you are interested in the topology of tokens which this
+ * Atom can match, 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; }
}
+