private static Exprent createConcatExprent(List<Exprent> lstOperands, Set<Integer> bytecode) {
    // build exprent to return
    Exprent func = lstOperands.get(0);

    for (int i = 1; i < lstOperands.size(); i++) {
      func = new FunctionExprent(FunctionExprent.FUNCTION_STR_CONCAT, Arrays.asList(func, lstOperands.get(i)), bytecode);
    }

    return func;
  }
private static Exprent createConcatExprent(List<Exprent> lstOperands, Set<Integer> bytecode)