X-Git-Url: http://git.megacz.com/?p=sbp.git;a=blobdiff_plain;f=src%2Fedu%2Fberkeley%2Fsbp%2FElement.java;h=33bfd8d7d08f5027e136aef1eaff959dfbf92ce7;hp=7e140f9a2f93b093a9ec2485cdd510d42aee3e9e;hb=5d18f5606c9296e6b0c5749f05fc68f358ace2f6;hpb=84a4a8204373b996105e69edf91d2f9fae7b4bcb

diff --git a/src/edu/berkeley/sbp/Element.java b/src/edu/berkeley/sbp/Element.java
index 7e140f9..33bfd8d 100644
--- a/src/edu/berkeley/sbp/Element.java
+++ b/src/edu/berkeley/sbp/Element.java
@@ -10,14 +10,9 @@ import java.lang.ref.*;
 /** the root superclass for all components of the grammar (terminals, nonterminals, literals, etc) */
 public abstract class Element {
 
-    abstract Topology toAtom();
-    public Topology noFollow() { return null; }
-    Forest epsilonForm() { throw new Error("no epsilon form: " + this); }
-    final boolean possiblyEpsilon(Walk.Cache cache)   {
-        Boolean ret = cache==null ? null : cache.possiblyEpsilon.get(this);
-        if (ret != null) return ret.booleanValue();
-        ret = new Walk.PossiblyEpsilon().walk(this) ? Boolean.TRUE : Boolean.FALSE;
-        if (cache != null) cache.possiblyEpsilon.put(this, ret);
-        return ret;
-    }
+    abstract StringBuffer toString(StringBuffer sb);
+
+    /** if this element always matches exactly one token, return a topology covering exactly those possible tokens, otherwise <tt>null</tt> */
+    Forest epsilonForm() { return null; }
+
 }