refactored Element.reachable()

darcs-hash:20060102055638-5007d-f8db0d2cb15d6da31acf84dd75b13ce59d171ec4.gz

diff --git a/src/edu/berkeley/sbp/Atom.java b/src/edu/berkeley/sbp/Atom.java
index 61f120d..524ab3a 100644 (file)
--- a/src/edu/berkeley/sbp/Atom.java
+++ b/src/edu/berkeley/sbp/Atom.java
@@ -12,8 +12,6 @@ public abstract class Atom<T extends Token> extends Element implements Topology<
 
     protected abstract Topology<T> top();
 
-    void reachable(HashSet<Sequence.Position> h) { /* do-nothing */ }
-
     public Topology toAtom() { return dup(); }
 
     /** equality is based on the underlying <tt>Topology</tt> */

diff --git a/src/edu/berkeley/sbp/Element.java b/src/edu/berkeley/sbp/Element.java
index b440257..7e140f9 100644 (file)
--- a/src/edu/berkeley/sbp/Element.java
+++ b/src/edu/berkeley/sbp/Element.java
@@ -10,9 +10,6 @@ import java.lang.ref.*;
 /** the root superclass for all components of the grammar (terminals, nonterminals, literals, etc) */
 public abstract class Element {
 
-    /** add all positions reachable from the start of this Element to @rp */
-    abstract void reachable(HashSet<Sequence.Position> rp);
-
     abstract Topology toAtom();
     public Topology noFollow() { return null; }
     Forest epsilonForm() { throw new Error("no epsilon form: " + this); }

diff --git a/src/edu/berkeley/sbp/Parser.java b/src/edu/berkeley/sbp/Parser.java
index 6986a4b..e707eac 100644 (file)
--- a/src/edu/berkeley/sbp/Parser.java
+++ b/src/edu/berkeley/sbp/Parser.java
@@ -13,6 +13,17 @@ public 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);
+    }
+
     //public Parser(          Topology top) { this(new Table(   top)); }
     //public Parser(String s, Topology top) { this(new Table(s, top)); }
 
@@ -80,7 +91,7 @@ public class Parser<T extends Token, R> {
         
         public HashSet<Position> closure()       {
             HashSet<Position> hp = new HashSet<Position>();
-            start0.reachable(hp);
+            reachable(start0, hp);
             return hp;
         }
         public Position firstPosition()          { return start0seq.firstp(); }
@@ -223,7 +234,7 @@ public class Parser<T extends Token, R> {
                     if (position.isLast() || !(position.element() instanceof Atom)) continue;
                     Atom a = (Atom)position.element();
                     HashSet<Position> hp = new HashSet<Position>();
-                    position.next().reachable(hp);
+                    reachable(position.next(), hp);
                     bag0.addAll(a.dup(), /*clo.walk()*/hp);
                 }
 
@@ -262,7 +273,7 @@ public class Parser<T extends Token, R> {
                     if (ys != null) {
                         for(Element y : ys) {
                             HashSet<Position> hp = new HashSet<Position>();
-                            p.next().reachable(hp);
+                            reachable(p.next(), hp);
                             move.addAll(y, hp);
                         }
                     }

diff --git a/src/edu/berkeley/sbp/Sequence.java b/src/edu/berkeley/sbp/Sequence.java
index e18f5ef..b332793 100644 (file)
--- a/src/edu/berkeley/sbp/Sequence.java
+++ b/src/edu/berkeley/sbp/Sequence.java
@@ -62,8 +62,6 @@ public abstract class Sequence extends Element implements Iterable<Element> {
         this.firstp = new Position(0);
     }
 
-    void reachable(HashSet<Position> h) { firstp().reachable(h); }
-
     Forest epsilonForm() { return firstp().rewrite(null); }
 
     protected abstract <T> Forest<T> postReduce(Token.Location loc, Forest<T>[] args);
@@ -74,12 +72,6 @@ public abstract class Sequence extends Element implements Iterable<Element> {
     /** the imaginary position before or after an element of a sequence; corresponds to an "LR item" */
     public class Position {
 
-        void reachable(HashSet<Position> h) {
-            if (h.contains(this)) return;
-            h.add(this);
-            if (element() != null) element().reachable(h);
-        }
-
                 final int      pos;
         private final Position next;
                 final Forest[] holder;

diff --git a/src/edu/berkeley/sbp/Union.java b/src/edu/berkeley/sbp/Union.java
index db0db7d..b000f95 100644 (file)
--- a/src/edu/berkeley/sbp/Union.java
+++ b/src/edu/berkeley/sbp/Union.java
@@ -16,8 +16,6 @@ public class Union extends Element implements Iterable<Sequence> {
 
     public Iterator<Sequence> iterator() { return alternatives.iterator(); }
 
-    void reachable(HashSet<Sequence.Position> h) { for(Sequence s : alternatives) s.reachable(h); }
-
     Topology toAtom() {
         if (alternatives.size()==0) throw new RuntimeException("cannot build an Atom from a Union with no productions");
         Topology ret = null;