X-Git-Url: http://git.megacz.com/?p=sbp.git;a=blobdiff_plain;f=src%2Fedu%2Fberkeley%2Fsbp%2FElement.java;h=f88ce87034116c22d58ac64dff9b5aa7f2f3db3a;hp=b199a23ca52f943964a5afb2a9002e94f42a54d4;hb=9ded11559a1b6f817e99355b1c9e2c88042e91d4;hpb=0a0227b9180534d2a431f3d6e08a398bde2244c4

diff --git a/src/edu/berkeley/sbp/Element.java b/src/edu/berkeley/sbp/Element.java
index b199a23..f88ce87 100644
--- a/src/edu/berkeley/sbp/Element.java
+++ b/src/edu/berkeley/sbp/Element.java
@@ -10,11 +10,11 @@ import java.lang.ref.*;
 /** the root superclass for all components of the grammar (terminals, nonterminals, literals, etc) */
 public abstract class Element {
 
-    /** add all positions reachable from the start of this Element to @rp */
-    abstract void reachable(HashSet<Sequence.Position> rp);
-
+    /** if this element always matches exactly one token, return a topology covering exactly those possible tokens, otherwise <tt>null</tt> */
+    abstract Topology toAtom();
+    public Topology toAtom0() { return toAtom(); }
     Forest epsilonForm() { throw new Error("no epsilon form: " + this); }
-    final boolean possiblyEpsilon(Walk.Cache cache)   {
+    final boolean possiblyEpsilon(Walk.Cache cache) {
         Boolean ret = cache==null ? null : cache.possiblyEpsilon.get(this);
         if (ret != null) return ret.booleanValue();
         ret = new Walk.PossiblyEpsilon().walk(this) ? Boolean.TRUE : Boolean.FALSE;