public object Get(string id)
        {
            object value = null; if (!TryGet(id, ref value))

            {
                throw Language.Error("undefined {0}", Syntax.ToString(id));
            }
            return(value);
        }
 public override string ToString()
 {
     var pair = (object[])Definition; return(string.Concat(Syntax.ToString(pair[0]), " => ", Syntax.ToString(pair[1])));
 }