X-Git-Url: http://git.megacz.com/?p=sbp.git;a=blobdiff_plain;f=src%2Fedu%2Fberkeley%2Fsbp%2FUnion.java;h=4de0bb4969c58512982b7977fda60c9c6eaeac05;hp=7370a6834307c40a3e70dc98017120274475d071;hb=1a249057cbfd2180910e46672eafee3af46ae470;hpb=77d1e5fd29be1ca529e71a4c011f5edea61588e8

diff --git a/src/edu/berkeley/sbp/Union.java b/src/edu/berkeley/sbp/Union.java
index 7370a68..4de0bb4 100644
--- a/src/edu/berkeley/sbp/Union.java
+++ b/src/edu/berkeley/sbp/Union.java
@@ -10,16 +10,24 @@ import java.lang.ref.*;
 /** an element which can produce one of several alternatives */
 public class Union extends Element implements Iterable<Sequence> {
 
+    /** display form for the Union (ie not including the RHS) */
     final String shortForm;
+
+    /** this is just a hint to use when printing out the grammar in visual form */
     final boolean synthetic;
+
+    /** the actual alternatives */
     private final List<Sequence> alternatives = new ArrayList<Sequence>();
 
     public Iterator<Sequence> iterator() { return alternatives.iterator(); }
-
-    void reachable(HashSet<Sequence.Position> h) { for(Sequence s : alternatives) s.reachable(h); }
+    public boolean contains(Sequence s) { return alternatives.contains(s); }
 
     /** adds an alternative */
-    public void add(Sequence s) { alternatives.add(s); }
+    public void add(Sequence s) {
+        alternatives.add(s);
+        for(Sequence n : s.needs) add(n);
+        for(Sequence n : s.hates) add(n);
+    }
 
     /**
      *  Since every cycle in a non-degenerate grammar contains at
@@ -36,6 +44,9 @@ public class Union extends Element implements Iterable<Sequence> {
         this.synthetic = synthetic;
     }
 
+    public static Union epsilon = new Union("()");
+    static { epsilon.add(Sequence.empty); }
+
     private Forest.Ref epsilonForm = null;
     Forest epsilonForm() {
         if (epsilonForm != null) return epsilonForm;