// ---------------------------------------------------------------
// VariableNode - Return the value associate with our name or
//                throw an exception if our name isn't found
// ---------------------------------------------------------------

import java.util.HashMap;
   
public class VariableNode extends Node
{
   public VariableNode(String name)
   {
      mName = name;
   }

   public double evaluate(HashMap<String, Double> env) throws Exception
   {
      Double theValue = env.get(mName);

      if(theValue == null)
         throw new Exception("Undefined variable: " + mName);

      return(theValue.doubleValue());
   }

   public String toString()
   {
      return(mName);
   }

   private String mName;
}