X-Git-Url: http://git.megacz.com/?p=sbp.git;a=blobdiff_plain;f=src%2Fedu%2Fberkeley%2Fsbp%2FSequence.java;h=b33279352a9a6b61c4cfd4bfa3e29629c3670e6f;hp=9586f728e1e5df391de200cfd00d1c090b751e2d;hb=888e9ccbab5f458a727c16da9d9291fd8951d909;hpb=2690f6c749f117a103c57d651d89f1b4fbf1316d

diff --git a/src/edu/berkeley/sbp/Sequence.java b/src/edu/berkeley/sbp/Sequence.java
index 9586f72..b332793 100644
--- a/src/edu/berkeley/sbp/Sequence.java
+++ b/src/edu/berkeley/sbp/Sequence.java
@@ -35,8 +35,11 @@ public abstract class Sequence extends Element implements Iterable<Element> {
 
     ////////////////////////////////////////////////////////////////////////////////
 
+    public Element noFollow = null;
+    public final Topology noFollow() { return noFollow==null ? null : noFollow.toAtom(); }
+
     Topology toAtom() {
-        if (elements.length!=1) return null;
+        if (elements.length!=1) throw new RuntimeException("cannot invoke toAtom() on a Sequence with " + elements.length + " elements: " + this);
         return elements[0].toAtom();
     }
 
@@ -59,8 +62,6 @@ public abstract class Sequence extends Element implements Iterable<Element> {
         this.firstp = new Position(0);
     }
 
-    void reachable(HashSet<Position> h) { firstp().reachable(h); }
-
     Forest epsilonForm() { return firstp().rewrite(null); }
 
     protected abstract <T> Forest<T> postReduce(Token.Location loc, Forest<T>[] args);
@@ -71,12 +72,6 @@ public abstract class Sequence extends Element implements Iterable<Element> {
     /** the imaginary position before or after an element of a sequence; corresponds to an "LR item" */
     public class Position {
 
-        void reachable(HashSet<Position> h) {
-            if (h.contains(this)) return;
-            h.add(this);
-            if (element() != null) element().reachable(h);
-        }
-
                 final int      pos;
         private final Position next;
                 final Forest[] holder;