X-Git-Url: http://git.megacz.com/?p=sbp.git;a=blobdiff_plain;f=src%2Fedu%2Fberkeley%2Fsbp%2FElement.java;h=7eb6a59b53f170689fdc395a8fae574165d38008;hp=7e140f9a2f93b093a9ec2485cdd510d42aee3e9e;hb=2c1c0293545f3d12c23220fd05c663e6aa3f3de1;hpb=84a4a8204373b996105e69edf91d2f9fae7b4bcb

diff --git a/src/edu/berkeley/sbp/Element.java b/src/edu/berkeley/sbp/Element.java
index 7e140f9..7eb6a59 100644
--- a/src/edu/berkeley/sbp/Element.java
+++ b/src/edu/berkeley/sbp/Element.java
@@ -7,17 +7,15 @@ import java.util.*;
 import java.lang.reflect.*;
 import java.lang.ref.*;
 
-/** the root superclass for all components of the grammar (terminals, nonterminals, literals, etc) */
-public abstract class Element {
+/** <font color=green>the root superclass for all components of the grammar (terminals, nonterminals, literals, etc)</font> */
+public abstract class Element implements SequenceOrElement {
+
+    /** sorry, you can't make up new, custom elements */
+    Element() { }
+
+    abstract StringBuffer toString(StringBuffer sb);
+
+    /** returns the Forest resulting from matching this element against the empty string */
+    Forest<?> epsilonForm() { throw new Error("element " + this + " has no epsilon form"); }
 
-    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;
-    }
 }