--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/main/gov/nasa/jpf/util/script/SequenceInterpreter.java	Fri Jan 23 10:14:01 2015 -0800
@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2014, United States Government, as represented by the
+ * Administrator of the National Aeronautics and Space Administration.
+ * All rights reserved.
+ *
+ * The Java Pathfinder core (jpf-core) platform is licensed under the
+ * Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ * 
+ *        http://www.apache.org/licenses/LICENSE-2.0. 
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and 
+ * limitations under the License.
+ */
+
+package gov.nasa.jpf.util.script;
+
+import gov.nasa.jpf.util.script.ScriptElementContainer.SECIterator;
+
+import java.io.StringReader;
+
+/**
+ * an interpreter that walks a ScriptElementContainer hierarchy, returning
+ * Events and Alternatives while expanding loops
+ */
+public class SequenceInterpreter implements Cloneable {
+
+  ScriptElementContainer.SECIterator top;
+
+  public SequenceInterpreter (ScriptElementContainer seq) {
+    top = seq.iterator();
+  }
+
+  void push (SECIterator it) {
+    it.prev = top;
+    top = it;
+  }
+
+  SECIterator pop () {
+    if (top != null) {
+      top = top.getPrev();
+    }
+    return top;
+  }
+
+  public ScriptElement getNext() {
+    if (top != null) {
+      ScriptElement e = top.next();
+      if (e != null) {
+        if ((e instanceof ScriptElementContainer) && !(e instanceof Alternative) ) {
+          push( ((ScriptElementContainer)e).iterator());
+          return getNext();
+        } else {
+          return e;
+        }
+      } else {
+        pop();
+        return (top != null) ? getNext() : null;
+      }
+    } else {
+      return null;
+    }
+  }
+
+  @Override
+  public Object clone() {
+    // has to deep copy all iterators
+
+    try {
+      SequenceInterpreter si = (SequenceInterpreter) super.clone();
+      if (top != null) {
+        si.top = (SECIterator)top.clone();
+      }
+      return si;
+    } catch (CloneNotSupportedException nonsense) {
+      return null; // we are a Cloneable, so we don't get here
+    }
+  }
+
+  public boolean isDone() {
+    return (top == null);
+  }
+
+  //---- test driver
+  public static void main (String[] args) {
+    //String s = "";
+    //String s = "a; b; c ";
+    //String s = "REPEAT 2 { e1, REPEAT 1 { r1, r2 }, e2 }";
+    //String s = "x, ANY {a1,a2}, y";
+    String s = "REPEAT 2 { start, ANY {a1,a2}, REPEAT 2 {r}, end }";
+
+
+    StringReader r = new StringReader(s);
+
+    try {
+      ESParser parser = new ESParser("test", r);
+      Script script = parser.parse();
+
+      SequenceInterpreter si = new SequenceInterpreter(script);
+
+      for (ScriptElement e = si.getNext(); e != null; e = si.getNext()) {
+        System.out.println(e);
+      }
+
+    } catch (Throwable t){
+      t.printStackTrace();
+    }
+  }
+}