static final WeakHashMap<Class, HashMap<S, Field>> getOpt_cache = newWeakHashMap();
static final new HashMap getOpt_special; // just a marker

static {
  getOpt_cache.put(Class.class, getOpt_special);
  getOpt_cache.put(S.class, getOpt_special);
}

static Object getOpt_cached(Object o, String field) ctex {
  if (o == null) ret null;

  Class c = o.getClass();
  HashMap<S, Field> map;
  synchronized(getOpt_cache) {
    map = getOpt_cache.get(c);
    if (map == null)
      map = getOpt_makeCache(c);
  }
  
  if (map == getOpt_special) {
    if (o instanceof Class)
      return getOpt((Class) o, field);
    /*if (o instanceof S)
      ret getOpt(getBot((S) o), field);*/
    if (o instanceof Map)
      ret ((Map) o).get(field);
  }
    
  Field f = map.get(field);
  if (f != null) ret f.get(o);
  ifclass DynamicObject
    if (o instanceof DynamicObject)
      ret ((DynamicObject) o).fieldValues.get(field);
  endif
  ret null;
}

// used internally - we are in synchronized block
static HashMap<S, Field> getOpt_makeCache(Class c) {
  HashMap<S, Field> map;
  if (isSubtypeOf(c, Map.class))
    map = getOpt_special;
  else {
    map = new HashMap;
    Class _c = c;
    do {
      for (Field f : _c.getDeclaredFields()) {
        f.setAccessible(true);
        S name = f.getName();
        if (!map.containsKey(name))
          map.put(name, f);
      }
      _c = _c.getSuperclass();
    } while (_c != null);
  }
  getOpt_cache.put(c, map);
  ret map;
}