// ---------------------------------------------------------------
// MethodNode - Subclass of Node representing a function call, all
//              our functions take one argument (a double) and
//              return a double, like: sin, cos, sqrt, etc.
// ---------------------------------------------------------------

import java.lang.reflect.Method;
import java.util.HashMap;
   
public class MethodNode extends Node
{
   public MethodNode(String name, Node arg)
   {
      mName = name;
      mArg  = arg;
   }

   public double evaluate(HashMap<String, Double> env) throws Exception
   {
      // -----------------------------------------------------
      // If mMethod is null, this is our first time through
      // evaluate - try to set that member variable
      // -----------------------------------------------------

      if(mMethod == null)
      {
         if((mMethod = mLookup.get(mName)) == null)
            throw new Exception("Unknown method: '" + mName + "'");
      }

      Object result = mMethod.invoke(null, mArg.evaluate(env));

      return(((Double)result).doubleValue());
   }

   public String toString()
   {
      return(mName + "(" + mArg.toString() + ")");
   }

   private String mName;
   private Node   mArg;
   private Method mMethod;

   private static HashMap<String, Method> mLookup =
      new HashMap<String, Method>();

   private static Method getMethod(String name)
   {
      Method theMethod = null;

      try
      {
         theMethod =
            Class.forName("java.lang.Math").getDeclaredMethod(name, double.class);
      }
      catch(Exception e)
      {
         System.out.println(e);
      }

      return(theMethod);
   }

   static
   {
      mLookup.put("abs",    getMethod("abs"));
      mLookup.put("acos",   getMethod("acos"));
      mLookup.put("asin",   getMethod("asin"));
      mLookup.put("cbrt",   getMethod("cbrt"));
      mLookup.put("ceil",   getMethod("ceil"));
      mLookup.put("cos",    getMethod("cos"));
      mLookup.put("cosh",   getMethod("cosh"));
      mLookup.put("exp",    getMethod("exp"));
      mLookup.put("floor",  getMethod("floor"));
      mLookup.put("log",    getMethod("log"));
      mLookup.put("log10",  getMethod("log10"));
      mLookup.put("round",  getMethod("round"));
      mLookup.put("sin",    getMethod("sin"));
      mLookup.put("sinh",   getMethod("sinh"));
      mLookup.put("sqrt",   getMethod("sqrt"));
      mLookup.put("tan",    getMethod("tan"));
      mLookup.put("tanh",   getMethod("tanh"));
   }
}