--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/main/gov/nasa/jpf/vm/choice/CompoundChoiceGenerator.java	Fri Jan 23 10:14:01 2015 -0800
@@ -0,0 +1,134 @@
+/*
+ * 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.vm.choice;
+
+import gov.nasa.jpf.vm.ChoiceGenerator;
+import gov.nasa.jpf.vm.ChoiceGeneratorBase;
+
+/**
+ * an abstract choice generator that is just a list of choice generators
+ */
+public abstract class CompoundChoiceGenerator<T> extends ChoiceGeneratorBase<T> {
+
+  //--- helper to implement ad hoc linked lists
+  protected class Entry {
+    ChoiceGenerator<T> cg;
+    Entry next;
+    
+    Entry (ChoiceGenerator<T> cg, Entry next){
+      this.cg = cg;
+      this.next = next;
+    }
+  }
+  
+  protected Entry base;
+  protected Entry cur;
+
+  protected CompoundChoiceGenerator (String id){
+    super(id);
+  }
+  
+  //--- to be called from derived ctors
+  
+  protected void setBase (ChoiceGenerator<T> cg){
+    base = cur = new Entry( cg, null);
+  }
+  
+  protected void add (ChoiceGenerator<T> cg){
+    base = cur = new Entry( cg, cur);
+  }
+  
+  //--- the public ChoiceGenerator interface
+  
+  @Override
+  public T getNextChoice () {
+    if (cur != null){
+      return cur.cg.getNextChoice();
+    } else {
+      return null;
+    }
+  }
+
+  @Override
+  public boolean hasMoreChoices () {
+    if (cur != null){
+      if (cur.cg.hasMoreChoices()){
+        return true;
+      } else {
+        for (Entry e = cur.next; e != null; e = e.next){
+          if (e.cg.hasMoreChoices()){
+            return true;
+          }
+        }
+        
+        return false;
+      }
+      
+    } else {
+      return false;
+    }
+  }
+
+  @Override
+  public void advance () {
+    if (cur != null){
+      if (cur.cg.hasMoreChoices()){
+        cur.cg.advance();
+      } else {
+        cur = cur.next;
+        advance();
+      }
+    }
+  }
+
+  @Override
+  public void reset () {
+    cur = base;
+    
+    for (Entry e = base; e != null; e = e.next){
+      e.cg.reset();
+    }
+  }
+
+  @Override
+  public int getTotalNumberOfChoices () {
+    int n = 0;
+    
+    for (Entry e = base; e != null; e = e.next){
+      n += e.cg.getTotalNumberOfChoices();
+    }
+    
+    return n;
+  }
+
+  @Override
+  public int getProcessedNumberOfChoices () {
+    int n=0;
+    
+    for (Entry e = base; e != null; e = e.next){
+      n += e.cg.getProcessedNumberOfChoices();
+      if (e == cur){
+        break;
+      }
+    }
+    
+    return n;
+  }
+
+}