X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=src%2Fedu%2Fberkeley%2Fsbp%2FForest.java;h=b2f4a2239f3b641e52ec7031ec466deed810e267;hb=61539aaf02d0537fd1df08b5d5bd03189992cf1e;hp=ee3bfbcf75c21c792419635b0e314b193db78886;hpb=2cca97362e80d5a3cd3e02d791a10cd7c6f6b29c;p=sbp.git

diff --git a/src/edu/berkeley/sbp/Forest.java b/src/edu/berkeley/sbp/Forest.java
index ee3bfbc..b2f4a22 100644
--- a/src/edu/berkeley/sbp/Forest.java
+++ b/src/edu/berkeley/sbp/Forest.java
@@ -1,3 +1,5 @@
+// Copyright 2006 all rights reserved; see LICENSE file for BSD-style license
+
 package edu.berkeley.sbp;
 import edu.berkeley.sbp.*;
 import edu.berkeley.sbp.Sequence.Position;
@@ -21,6 +23,7 @@ public abstract class Forest<NodeType> implements GraphViz.ToGraphViz {
     public void expand(HashSet<Tree<NodeType>> ht) { expand(ht, new HashSet<Forest<NodeType>>(), null); }
 
     static <NodeType> Forest<NodeType> create(Input.Region loc, NodeType head, Forest<NodeType>[] children, boolean lift) {
+        if (loc == null) throw new Error();
         return new One<NodeType>(loc, head, children, lift);
     }
 
@@ -126,7 +129,6 @@ public abstract class Forest<NodeType> implements GraphViz.ToGraphViz {
     /** An "ambiguity node"; this is immutable once it has been "looked at" */
     static class Many<NodeType> extends Forest<NodeType> {
 
-        HashSet<GSS.Phase.Node> parents = new HashSet<GSS.Phase.Node>();
         private FastSet<Forest<NodeType>> hp = new FastSet<Forest<NodeType>>();
         private boolean touched = false;
 
@@ -155,6 +157,14 @@ public abstract class Forest<NodeType> implements GraphViz.ToGraphViz {
         
         void gather(HashSet<Forest<NodeType>> ht) {
             touched();
+
+            // FIXME: do something more sensible here
+            if (ht.contains(this)) {
+                System.err.println("WARNING: grammar produced a circular forest\n" + this);
+                //throw new Error("grammar produced a circular forest:\n" + this);
+                return;
+            }
+
             ht.add(this);
             for(Forest<NodeType> f : hp) f.gather(ht);
         }