+ static class EquivalentTo extends Walk<HashSet<Sequence>> {
+ private final Sequence s;
+ private final HashSet<Sequence> eq = new HashSet<Sequence>();
+ public final HashSet<Sequence> walk() { return walk(s); }
+ public EquivalentTo(Sequence e, Cache c) {
+ super(c); this.s = e;
+ }
+ public HashSet<Sequence> bottom(SequenceOrElement e) { return eq; }
+ public HashSet<Sequence> walkSequence(Sequence seq) {
+ eq.add(seq);
+ Position p = seq.firstp();
+ for(; !p.isLast(); p = p.next()) {
+ if (!p.isLast() && isRightNullable(p.next()))
+ walk(p.element());
+ if (!c.possiblyEpsilon(p.element())) break;
+ }
+ return eq;
+ }
+ public HashSet<Sequence> walkAtom(Atom r) {
+ return eq;
+ }
+ private boolean isRightNullable(Position p) {
+ if (p.isLast()) return true;
+ if (!c.possiblyEpsilon(p.element())) return false;
+ return isRightNullable(p.next());
+ }
+ }
+