X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=src%2Fedu%2Fberkeley%2Fsbp%2FWalk.java;h=cd991e889028d64f1f12c28b72635837f7824bbf;hb=aaa5d101e054dc548e7ef7831b1fcb7913a4d4d4;hp=22ef52e66e4214b8f5dfdaab44522cf8ab1144ab;hpb=21da21b94e794fa4d7c7207327764895d92ea528;p=sbp.git

diff --git a/src/edu/berkeley/sbp/Walk.java b/src/edu/berkeley/sbp/Walk.java
index 22ef52e..cd991e8 100644
--- a/src/edu/berkeley/sbp/Walk.java
+++ b/src/edu/berkeley/sbp/Walk.java
@@ -75,9 +75,9 @@ abstract class Walk<T> {
     }
 
 
-    // Token-Set //////////////////////////////////////////////////////////////////////////////
+    // Input-Set //////////////////////////////////////////////////////////////////////////////
 
-    static abstract class WalkTokenSet<Tok extends Token> extends Walk<Topology<Tok>> {
+    static abstract class WalkTokenSet<Tok extends Input> extends Walk<Topology<Tok>> {
         public Topology<Tok> cs;
         public WalkTokenSet(Topology<Tok> cs)          { this.cs = cs; }
         public WalkTokenSet(Topology<Tok> cs, Cache c) { super(c); this.cs = cs; }
@@ -85,18 +85,18 @@ abstract class Walk<T> {
         public Topology<Tok> walkAtom(Atom r)          { cs = cs.union(r); return cs; }
     }
 
-    class First<Tok extends Token> extends WalkTokenSet<Tok> {
+    static class First<Tok extends Input> extends WalkTokenSet<Tok> {
         public First(Topology<Tok> cs, Walk.Cache cache) { super(cs, cache); }
         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;
         }
     }
 
-    static class Follow<Tok extends Token> extends WalkTokenSet<Tok> {
+    static class Follow<Tok extends Input> extends WalkTokenSet<Tok> {
         private final Element me;
         private final HashSet<Element> all;
         private boolean eof = false;
@@ -129,8 +129,8 @@ abstract class Walk<T> {
                 Sequence a = (Sequence)x;
                 Position mp = null;
                 for(Position pos = a.firstp(); pos != null && !pos.isLast(); pos = pos.next()) {
-                    if (matched) cs = cs.union(new First<Tok>(cs.empty(), c).walk(pos.element()));
-                    if (pos.isLast()) { matched = (matched && pos.element().possiblyEpsilon(c)); continue; }
+                    if (matched) cs = cs.union(c.first(pos.element(), cs.empty()));
+                    if (pos.isLast()) { matched = (matched && c.possiblyEpsilon(pos.element())); continue; }
                     boolean good = false;
                     if (e instanceof Atom) {
                         Topology top = c.atoms.get(pos.element());
@@ -149,7 +149,7 @@ abstract class Walk<T> {
 
             if (e instanceof Sequence) {
                 Sequence s = (Sequence)e;
-                if (s.noFollow() != null) cs = cs.minus(s.noFollow());
+                if (s.follow() != null) cs = cs.intersect(s.follow());
             }
 
             if (c != null && e==me) {
@@ -172,5 +172,16 @@ abstract class Walk<T> {
         public HashMap<Element,Topology> follow = new HashMap<Element,Topology>();
         public HashMapBag<Element,Element>  ys = new HashMapBag<Element,Element>();
         public HashMap<Element,Topology> atoms = new HashMap<Element,Topology>();
+        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;
+        }
     }
 }