1 package edu.berkeley.sbp;
4 import java.lang.reflect.*;
5 import java.lang.ref.*;
6 import edu.berkeley.sbp.util.*;
7 import edu.berkeley.sbp.*;
8 import edu.berkeley.sbp.*;
10 /** an element which matches exactly one input token */
11 public abstract class Atom<T extends Token> extends Element {
13 private final Topology<T> rt;
15 public Atom(Topology<T> rt) { this.rt = rt; }
17 Topology<T> top() { return rt; }
19 void reachable(HashSet<Sequence.Position> h) { /* do-nothing */ }
21 /** equality is based on the underlying <tt>Topology</tt> */
22 public int hashCode() { return rt.hashCode(); }
24 /** equality is based on the underlying <tt>Topology</tt> */
25 public boolean equals(Object o) { return o != null && o instanceof Atom && ((Atom)o).rt.equals(rt); }
27 /** declared abstract to force subclasses to override it in a useful manner */
28 public abstract String toString();