eliminated Parser.Table.Top

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

diff --git a/src/edu/berkeley/sbp/Parser.java b/src/edu/berkeley/sbp/Parser.java
index e8e0dc8..5b31b31 100644 (file)
--- a/src/edu/berkeley/sbp/Parser.java
+++ b/src/edu/berkeley/sbp/Parser.java
@@ -13,17 +13,6 @@ public abstract class Parser<T extends Token, R> {
 
     private final Table pt;
 
-    private static void reachable(Element e, HashSet<Position> h) {
-        if (e instanceof Atom) return;
-        for(Sequence s : ((Union)e))
-            reachable(s.firstp(), h);
-    }
-    private static void reachable(Position p, HashSet<Position> h) {
-        if (h.contains(p)) return;
-        h.add(p);
-        if (p.element() != null) reachable(p.element(), h);
-    }
-
     /**
      *  create a parser to parse the grammar with start symbol <tt>u</tt>
      */
@@ -82,12 +71,10 @@ public abstract class Parser<T extends Token, R> {
 
     // Table //////////////////////////////////////////////////////////////////////////////
 
-    static class Top extends Union { public Top() { super("0"); } }
-
     /** an SLR(1) parse table which may contain conflicts */
     static class Table {
 
-        private final Union start0 = new Top();
+        private final Union start0 = new Union("0");
         private final Sequence start0seq;
         
         public final Walk.Cache cache = new Walk.Cache();
@@ -97,8 +84,6 @@ public abstract class Parser<T extends Token, R> {
             reachable(start0, hp);
             return hp;
         }
-        public Position firstPosition()          { return start0seq.firstp(); }
-        public Position lastPosition()           { Position ret = start0seq.firstp(); while(!ret.isLast()) ret = ret.next(); return ret; }
         
         private void walk(Element e, HashSet<Element> hs) {
             if (e==null) return;
@@ -137,12 +122,16 @@ public abstract class Parser<T extends Token, R> {
         public Table(Topology top) { this("s", top); }
         public Table(String startSymbol, Topology top) { this(new Union(startSymbol), top); }
         public Table(Union u, Topology top) {
+            cache.eof.put(start0, true);
             start0seq = new Sequence.Singleton(u, null, null);
+            cache.eof.put(start0seq, true);
             start0.add(start0seq);
 
             // construct the set of states
             HashMap<HashSet<Position>,State>   all_states    = new HashMap<HashSet<Position>,State>();
             HashSet<Element>                   all_elements  = walk();
+            all_elements.add(start0);
+            all_elements.add(start0seq);
             for(Element e : all_elements)
                 cache.ys.put(e, new Walk.YieldSet(e, cache).walk());
             this.start = new State(closure(), all_states, all_elements);
@@ -152,7 +141,7 @@ public abstract class Parser<T extends Token, R> {
                 for(Position p : state.hs) {
 
                     // the Grammar's designated "last position" is the only accepting state
-                    if (p==lastPosition())
+                    if (p==start0seq.firstp().next())
                         state.accept = true;
 
                     // FIXME: how does right-nullability interact with follow restrictions?
@@ -238,7 +227,7 @@ public abstract class Parser<T extends Token, R> {
                     Atom a = (Atom)position.element();
                     HashSet<Position> hp = new HashSet<Position>();
                     reachable(position.next(), hp);
-                    bag0.addAll(a, /*clo.walk()*/hp);
+                    bag0.addAll(a, hp);
                 }
 
                 // Step 1b: for each _minimal, contiguous_ set of characters having an identical next-position
@@ -348,4 +337,19 @@ public abstract class Parser<T extends Token, R> {
     }
 
     private static final Forest[] emptyForestArray = new Forest[0];
+
+
+    // Helpers //////////////////////////////////////////////////////////////////////////////
+
+    private static void reachable(Element e, HashSet<Position> h) {
+        if (e instanceof Atom) return;
+        for(Sequence s : ((Union)e))
+            reachable(s.firstp(), h);
+    }
+    private static void reachable(Position p, HashSet<Position> h) {
+        if (h.contains(p)) return;
+        h.add(p);
+        if (p.element() != null) reachable(p.element(), h);
+    }
+
 }