X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=src%2Fedu%2Fberkeley%2Fsbp%2FSequence.java;h=ac34264b3a527fe16c9fb6790ab802e4aab2840d;hb=3473141880127c6aa52d094d51739e5eb67f1703;hp=610af5879d4daa47b54bbf360def27de2d7ee97d;hpb=526da96dd06e152d194ec92c9ef9df6085a1251b;p=sbp.git

diff --git a/src/edu/berkeley/sbp/Sequence.java b/src/edu/berkeley/sbp/Sequence.java
index 610af58..ac34264 100644
--- a/src/edu/berkeley/sbp/Sequence.java
+++ b/src/edu/berkeley/sbp/Sequence.java
@@ -87,7 +87,15 @@ public abstract class Sequence extends Element implements Iterable<Element> {
     // Position //////////////////////////////////////////////////////////////////////////////
 
     /** the imaginary position before or after an element of a sequence; corresponds to an "LR item" */
-    public class Position {
+    public class Position implements IntegerMappable {
+
+        private Forest zero = null;
+        public Forest zero() {
+            if (zero != null) return zero;
+            if (pos > 0) throw new Error();
+            return zero = rewrite(null);
+        }
+
 
                 final int      pos;
         private final Position next;
@@ -100,11 +108,6 @@ public abstract class Sequence extends Element implements Iterable<Element> {
         }
 
         boolean isFirst() { return pos==0; }
-        boolean isRightNullable(Walk.Cache cache) {
-            if (isLast()) return true;
-            if (!element().possiblyEpsilon(cache)) return false;
-            return next().isRightNullable(cache);
-        }
 
         /** the element immediately after this Position, or null if this is the last Position */
         public Element  element() { return pos>=elements.length ? null : elements[pos]; }
@@ -118,7 +121,7 @@ public abstract class Sequence extends Element implements Iterable<Element> {
         /** true iff this Position is the last one in the sequence */
         public boolean isLast() { return next()==null; }
 
-        // Reduction /////////////////////////////////////////////////////////////////////////////////
+        // Position /////////////////////////////////////////////////////////////////////////////////
 
         final <T> Forest<T> rewrite(Token.Location loc) {
             if (this==firstp()) return epsilonForm();
@@ -142,14 +145,16 @@ public abstract class Sequence extends Element implements Iterable<Element> {
             for(Position p = Sequence.this.firstp(); p != null; p = p.next()) {
                 ret.append(' ');
                 if (p==this) ret.append(" | ");
-                if (p.element()!=null) ret.append(p.element().possiblyEpsilon(null) ? "["+p.element()+"]" : p.element());
+                if (p.element()!=null) ret.append(p.element());
                 else                   ret.append(' ');
             }
             ret.append("}>");
             return ret.toString();
         }
+        private final int idx = master_position_idx++;
+        public int toInt() { return idx; }
     }
-
+    private static int master_position_idx = 0;
 
     // toString //////////////////////////////////////////////////////////////////////////////
 
@@ -170,7 +175,7 @@ public abstract class Sequence extends Element implements Iterable<Element> {
         private final Object result;
         public Constant(Element[] e, Object result, HashSet<Sequence> and, HashSet<Sequence> not) { super(e, and, not); this.result = result; }
         public <T> Forest<T> postReduce(Token.Location loc, Forest<T>[] args) {
-            return (Forest<T>)Forest.leaf(loc, result, this);
+            return (Forest<T>)Forest.leaf(loc, result);
         }
         static class Drop extends Constant {
             public Drop(Element[] e, HashSet<Sequence> and, HashSet<Sequence> not, boolean lame) {
@@ -185,7 +190,7 @@ public abstract class Sequence extends Element implements Iterable<Element> {
         private final int idx;
         public Singleton(Element e, HashSet<Sequence> and, HashSet<Sequence> not) { this(new Element[] { e }, 0, and, not); }
         public Singleton(Element[] e, int idx, HashSet<Sequence> and, HashSet<Sequence> not) { super(e, and, not); this.idx = idx; }
-        public <T> Forest<T> postReduce(Token.Location loc, Forest<T>[] args) { return (Forest<T>)Forest.singleton(loc, args[idx], this); }
+        public <T> Forest<T> postReduce(Token.Location loc, Forest<T>[] args) { return (Forest<T>)Forest.singleton(loc, args[idx]); }
     }
 
     public static class Unwrap extends Sequence {
@@ -194,13 +199,13 @@ public abstract class Sequence extends Element implements Iterable<Element> {
         public Unwrap(Element[] e, boolean[] drops, HashSet<Sequence> and, HashSet<Sequence> not) { super(e, and, not); this.drops = drops; }
         public <T> Forest<T> postReduce(Token.Location loc, Forest<T>[] args) {
             for(int i=0; i<args.length; i++) if (args[i]==null) throw new Error();
-            if (drops==null) return Forest.create(loc, null, args, this, true, false);
+            if (drops==null) return Forest.create(loc, null, args, true, false);
             int count = 0;
             for(int i=0; i<drops.length; i++) if (!drops[i]) count++;
             Forest<T>[] args2 = new Forest[count];
             int j = 0;
             for(int i=0; i<args.length; i++) if (!drops[i]) args2[j++] = args[i];
-            return Forest.create(loc, null, args2, this, true, false);            
+            return Forest.create(loc, null, args2, true, false);            
         }
     }
 
@@ -220,7 +225,7 @@ public abstract class Sequence extends Element implements Iterable<Element> {
             int j = 0;
             for(int i=0; i<args.length; i++) if (!drops[i]) args2[j++] = args[i];
             //System.out.println("reduce \""+tag+"\"");
-            return Forest.create(loc, (T)tag, args2, this, false, false);
+            return Forest.create(loc, (T)tag, args2, false, false);
         }
         public StringBuffer toString(StringBuffer sb, boolean spacing) {
             int len = sb.length();