我在设计一个复杂的图像嵌入命令时发现了这个问题，从下面代码中定义的各种辅助命令的名称中或许可以猜到这一点：代码的结构也反映了设计的复杂性。\multipicts下面的命令通过使用命令接受可变数量的参数 \forcsvlist。每个参数由一对用花括号括起来的逗号分隔的变量组成。第一个变量是 .jpg、.png、.ps 或 .eps 图像的名称，而第二个变量是定义同一图像的裁剪边距的字符串：这些变量分别作为\showpicname和传递\showcroplims命令传递给\includegraphics命令，方式如下
\includegraphics[width=\linewidth,keepaspectratio,trim=\noexpand\showcroplims, clip]{\noexpand\showpicname}
但是，下面的测试代码并没有做到这一点，它仅限于定义\showpicname和\showcroplims
\documentclass[a4paper, 12pt, oneside]{paper} % Preamble
% structure settings
\usepackage{etoolbox}
\usepackage{ifthen}
\newcounter{cmdargs} % Number of variable arguments for user defined commands
\newcounter{argnum} % index of an argument in a list
\newcommand{\showpicname}{{\picn@me}} % First parameter of the argument couple to be extracted
\newcommand{\showcroplims}{{\crop@lims}} % Second parameter of the argument couple to be extracted
\pagestyle{empty}
\newcommand*{\argscount}[1]{%
\stepcounter{cmdargs}
}
\newcommand*{\xpargs}[1]{% Arguments expander
\stepcounter{argnum}
\ifthenelse{\value{argnum}=1}
{\gdef\picn@me{#1}} % If the value of argnum is 1 then the parameter parsed is the picture name
{\gdef\crop@lims{#1}} % Otherwise it is the crop margin string
}
\newcommand*{\addimage}[1]{% Image insertion (via multipicts)
\setcounter{argnum}{0}
\forcsvlist{\xpargs}{#1}\\
The argument is\ \{#1\}:\\
The parameters of the argument are\ \noexpand{\showpicname}\ and\ \noexpand{\showcroplims}.\\
\setcounter{argnum}{0}
}
\newcommand{\multipicts}[1]{% Multipicture environment
\setcounter{cmdargs}{0}
\forcsvlist{\argscount}{#1} % Count the arguments of invocation
\forcsvlist{\addimage}{#1}\\% Embed the "image"
This is a test: the number of iterations done is \arabic{cmdargs}.
}
\begin{document}
\noindent
First call of the macro:\\
\noindent
\multipicts{{a,0.5cm 0.5cm 0.5cm 0.5cm},{b,c},{c,d},{d,e}}\\[2ex]
\noindent
Second call of the macro:\\
\noindent
\multipicts{{2016-05-11_Valvola_intercettazione_lucchettata-low_dim.jpg,0.5cm 0.5cm 0.5cm 0.5cm},{b,c},{c,d},{d,e}}
\end{document}
下图显示了此代码的编译结果
当\pic@name是一个简单的字母字符时，一切似乎都很好，而当它是真正的图片名称时，命令就会中断。下划线“_”似乎被解释为数学模式命令，尽管\noexpand为了避免这种情况而放置了下划线。总之，我的问题是：我怎样才能让这样的命令表现得像简单的字符串？
答案1
我算出了对 egreg 的问题的评论中的建议，即我\detokenize在需要的地方使用了命令：特别地，请注意，我必须使用命令两次，一次是在宏中\pic@name分配的值时，一次是在解析的参数时，以便“停用”这对参数。\gdef\xpargs\addimage
\documentclass[a4paper, 12pt, oneside]{paper}
% Preamble
% structure settings
\usepackage{calc} % programmer's tools of the trade
\usepackage{etoolbox} % programmer's tools of the trade, II
\usepackage{ifthen} % programmer's tools of the trade, III
\newcounter{cmdargs} % Number of variable arguments for user defined commands
\newcounter{argnum} % index of an argument in a list
\newcommand{\showpicname}{{\picn@me}} % First parameter of the argument couple to be extracted
\newcommand{\showcroplims}{{\crop@lims}} % Second parameter of the argument couple to be extracted
\pagestyle{empty}
\newcommand*{\argscount}[1]{%
\stepcounter{cmdargs}
}
\newcommand*{\xpargs}[1]{% Arguments expander
\stepcounter{argnum}
\ifthenelse{\value{argnum}=1}
{\gdef\picn@me{\detokenize{#1}}} % If the value of argnum is 1 then the parameter parsed is the first one
{\gdef\crop@lims{#1}} % Otherwise it is the second
}
\newcommand*{\addimage}[1]{% Image insertion (via multipicts)
\setcounter{argnum}{0}
\forcsvlist{\xpargs}{#1}\\
The argument is\ \{\detokenize{#1}\}:\\
The parameters of the argument are \showpicname\ and \showcroplims.\\
\setcounter{argnum}{0}
}
\newcommand{\multipicts}[1]{% Multipicture environment
\setcounter{cmdargs}{0}
\forcsvlist{\argscount}{#1} % Count the arguments of invocation
\forcsvlist{\addimage}{#1}\\% Embed the "image"
This is a test: the number of iterations done is \arabic{cmdargs}.
}
\begin{document}
\noindent
First call of the macro:\\
\noindent
\multipicts{{a,0.5cm 0.5cm 0.5cm 0.5cm},{b,c},{c,d},{d,e}}\\[2ex]
\noindent
Second call of the macro:\\
\noindent
\multipicts{{2016-05-11_Valvola_intercettazione_lucchettata-low_dim.jpg,0.5cm 0.5cm 0.5cm 0.5cm},{b,c},{c,d},{d,e}}
\end{document}
这是我运行代码后得到的结果：
最后，我必须说，现在我完全同意 egreg 的观点：使用 LaTEX 时，更简单的方法是不要使用虚拟程序来测试算法，而是直接尝试。在我看来，这是 LaTEX 命令特殊结构的结果。