checkpoint

[sbp.git] / src / edu / berkeley / sbp / Walk.java

diff --git a/src/edu/berkeley/sbp/Walk.java b/src/edu/berkeley/sbp/Walk.java
index 04e36ae..8c6ecae 100644 (file)
--- 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());
         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;
         }
             }
             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()));
                 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());
                     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);
         }
         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;
+        }

     }
 }
     }
 }