重新定义环境内的命令

Question

如果重新定义不使用参数，则环境内部命令的重新定义可以正常工作，但如果在新定义中使用了参数，则重新定义会失败。

错误信息是：

\inversion 定义中的参数数量非法。

（倒置是所涉及的环境，仅被定义，尚未使用）

以下是两个例子

%% FIRST
\documentclass{minimal} 
%
% a command with two arguments,
% the two argument are printed in natural order
\newcommand{\printtwoarg}[2]{TwoArg: #1 #2}
% the new command is redefined INSIDE a new environment, WITHOUT using the arguments 
\newenvironment{noprint}{\renewcommand{\printtwoarg}[2]{TwoArg: \relax}}{\relax}
%% the new command is redefined INSIDE a new environment: the arguments are printed in inverted order
%%\newenvironment{inversion}{\renewcommand{\printtwoarg}[2]{TwoArg: #2 #1}}{\relax}
%
\begin{document}
Using the new command:\\
\printtwoarg{TheFirst}{TheSecond}  \\
%
\begin{noprint}
Using the new command INSIDE the new environment:\\
\printtwoarg{TheFirst}{TheSecond}  \\
\end{noprint}
%
... and OUTSIDE again:\\
\printtwoarg{TheFirst}{TheSecond}  \\
%
\end{document}

进而

%% SECOND
\documentclass{minimal} 
%
% a command with two arguments,
% the two argument are printed in natural order
\newcommand{\printtwoarg}[2]{TwoArg: #1 #2}
% the new command is redefined INSIDE a new environment, WITHOUT using the arguments 
\newenvironment{noprint}{\renewcommand{\printtwoarg}[2]{TwoArg: \relax}}{\relax}
% the new command is redefined INSIDE a new environment: the arguments are printed in inverted order
\newenvironment{inversion}{\renewcommand{\printtwoarg}[2]{TwoArg: #2 #1}}{\relax}
%
\begin{document}
Using the new command:\\
\printtwoarg{TheFirst}{TheSecond}  \\
%
\begin{noprint}
Using the new command INSIDE the new environment:\\
\printtwoarg{TheFirst}{TheSecond}  \\
\end{noprint}
%
... and OUTSIDE again:\\
\printtwoarg{TheFirst}{TheSecond}  \\
%
\end{document}

第一个例子运行良好，第二个例子失败。区别在于定义环境反转的未注释行。

我真的不知道这是一个难题还是一个小问题！！

谨致问候并提前致谢

巴蒂斯塔·本乔利尼