public void execute(string command)
 {
     for (int i = 0; i < _functions.Count; i++)
     {
         RPN_Function pf = _functions[i];
         if (!pf.checkName(command))
         {
             continue;
         }
         int operand = pf.Name().Length;
         pf.execute(_parent, command.Substring(operand));
         pf.advancePC(_parent);
         return;
     }
     rpnStack.setLabel(0, command);
     progMem.incrementCounter();
 }