X-Git-Url: http://git.megacz.com/?p=sbp.git;a=blobdiff_plain;f=src%2Fedu%2Fberkeley%2Fsbp%2FWalk.java;h=8c6ecae17d897509e18d764dddb2346275f46135;hp=04e36aeb47f1aae6e3db58083fdeb67a80b65cd1;hb=5d18f5606c9296e6b0c5749f05fc68f358ace2f6;hpb=1a249057cbfd2180910e46672eafee3af46ae470

diff --git a/src/edu/berkeley/sbp/Walk.java b/src/edu/berkeley/sbp/Walk.java
index 04e36ae..8c6ecae 100644
--- a/src/edu/berkeley/sbp/Walk.java
+++ b/src/edu/berkeley/sbp/Walk.java
@@ -90,7 +90,7 @@ abstract class Walk<T> {
         public Topology<Tok> sequence(Sequence seq) {
             for(Position p = seq.firstp(); p!=null && !p.isLast(); p = p.next()) {
                 walk(p.element());
-                if (!p.element().possiblyEpsilon(c)) break;
+                if (!c.possiblyEpsilon(p.element())) break;
             }
             return cs;
         }
@@ -130,7 +130,7 @@ abstract class Walk<T> {
                 Position mp = null;
                 for(Position pos = a.firstp(); pos != null && !pos.isLast(); pos = pos.next()) {
                     if (matched) cs = cs.union(c.first(pos.element(), cs.empty()));
-                    if (pos.isLast()) { matched = (matched && pos.element().possiblyEpsilon(c)); continue; }
+                    if (pos.isLast()) { matched = (matched && c.possiblyEpsilon(pos.element())); continue; }
                     boolean good = false;
                     if (e instanceof Atom) {
                         Topology top = c.atoms.get(pos.element());
@@ -175,5 +175,13 @@ abstract class Walk<T> {
         public <Tok extends Input> Topology<Tok> first(Element e, Topology<Tok> empty) {
             return new Walk.First<Tok>(empty, this).walk(e);
         }
+        final boolean possiblyEpsilon(Element e) {
+            Walk.Cache cache = this;
+            Boolean ret = possiblyEpsilon.get(e);
+            if (ret != null) return ret.booleanValue();
+            ret = new Walk.PossiblyEpsilon().walk(e) ? Boolean.TRUE : Boolean.FALSE;
+            possiblyEpsilon.put(e, ret);
+            return ret;
+        }
     }
 }