add comment to Element

[sbp.git] / src / edu / berkeley / sbp / Element.java

diff --git a/src/edu/berkeley/sbp/Element.java b/src/edu/berkeley/sbp/Element.java
index 4ccde61..35678ab 100644 (file)
--- a/src/edu/berkeley/sbp/Element.java
+++ b/src/edu/berkeley/sbp/Element.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.util.*;
 import edu.berkeley.sbp.*;
@@ -8,14 +10,15 @@ import java.lang.reflect.*;
 import java.lang.ref.*;
 
 /** <font color=green>the root superclass for all components of the grammar (terminals, nonterminals, literals, etc)</font> */
-public abstract class Element {
+public abstract class Element implements SequenceOrElement {
 
     /** sorry, you can't make up new, custom elements */
     Element() { }
 
+    /** a more verbose version of toString() which should show the entire grammar */
     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"); }
+    Forest<?> epsilonForm(Input.Region loc) { throw new Error("element " + this + " has no epsilon form"); }
 
 }