我的收藏以供参考

Question

我一直在研究 TeX 原语，特别是 catcodes，以处理各种 LaTeX 情况（并扩展我的能力）。

我在以下帮助下创建了一个 token 吞噬者https://tex.stackexchange.com/a/33536/13552

为什么我在类别代码列表中看不到任何数字 10？

测试是否安全\@empty？如果是，使用 \g@addto@macro{\tempa}{\fbox{ }}%

\documentclass{article}
\begin{document}
\makeatletter
\def\scanfunction#1{#1}% Don't know why this is here
\let\tempa\@empty
\def\scan@letters#1#2{% https://tex.stackexchange.com/a/33536/13552
   \bgroup\catcode`\ \active \let\ \fbox{ }\egroup%Try changing space to visible box
   \def\getcategory##1{\the\catcode`##1}% ` changes char into ASCI number required for \catcode
   \def\currcatcode{\getcategory{#1}}% put everything into unified token for \if
   \currcatcode, % spurious space intentional % first character missing
   \if 10\currcatcode%
     \fbox{#2}% if catcode 10 fed, print it as a box
   \fi
   \g@addto@macro{\tempa}{#1\hskip 0pt plus 1sp minus 1sp}%
   \ifx#2\@empty%\@empty is what the end of the line will look like ^^M?
   \else
     \expandafter\scan@letters % recall yourself using #2 until this conditional becomes true
   \fi
#2}

\def\scan#1{%
  %\catcode"0020 11 % Tried changing space to catcode 11
  %\the\catcode"0020 % Test to ensure change happened
  \scan@letters #1\@empty
}

\makeatother
\scan{  mac::exception  ==  }
% \scan{     } % crashes with "Improper alphabetic constant."
\begin{itemize}
  \item \tempa
\end{itemize}
\end{document}

当然，我期望\scan{ mac::exception == }

10, 10, 11, 11, 11, 12, 12, 11, 11, 11, 11, 11, 11, 11, 11, 11, 10, 10, 12, 12, 10, 10,

我的收藏以供参考

显然，它是有可能看到 10。

\the\catcode`\

结果：13（错误地预期为10）

\the\catcode`\ %

结果：10

\the\catcode"0020

结果：10

• 测试标记是否是控制序列

---

2016 年 6 月 24 日更新实用解决方案

知道这一点也许很有用，所以我把它放在这里。使用上下文和 David Carlisle 的回答来理解，\afterassignment以便我可以测试第 10 类（空格），我修改了我的代码，在每个非空格字符后添加粘连，这样 LaTeX 换行机制就会在以下情况下触发：

• 所有字符框的总宽度 =\textwidth

样本

\documentclass{article}
\usepackage{fontspec}
\newfontfamily\macmonofont{Inconsolatazi4-Regular.otf}
%\makeatletter % or \catcode"0040=11
\def\macmono#1{\xscan#1\relax}% calls xscan which looks ahead one token, #1
\def\xscan{\afterassignment\xxscan\let\token= }% assign single token to \token and call \xxscan
\def\xxscan{%
\macmonofont% apply mono font
\ifx\token\relax\normalfont\else%test for end-of-line or end of group and switch back to normal font
  \ifcat\token\space%
    \token% token is catcode 10
    \spaceskip=.5em% remove glue from space for fixed-width space
    \xspaceskip=.5em% remove glue from space for fixed-width space
  \else%
    \token\hskip 0pt plus 1sp minus 1sp % add glue to any non-catcode 10 (space)
   \fi
\expandafter\xscan
\fi}
%\makeatother % or \catcode"0040=12
\parindent=0pt % remove firstpar autoindent
\obeylines% insert \par after each end-of-line (^^M)

\begin{document}
\begin{itemize}
\item Some random error created by C++: \macmono{mac::IOException [File: sharecpp/trunk/PROJECTS/SpecialOps/B/Build/Implementation/Library/GenerateDocumentation.cpp, Line: 999]
    Found documentation overview begin marker more than once in DocumentationManual!
mac::IOException [File: sharecpp/trunk/PROJECTS/SpecialOps/B/Build/Implementation/Library/DocumentationThread.cpp, Line: 934]
    Processing of DocumentationManual failed while generating DocumentationOverview!} and some trailing test to make sure font changing works.  \end{itemize}
\end{document}

输出

Answer 1

无括号的 catcode 10 个字符永远不会被视为无界参数，因此您可以

\def\foo#1#2#3{...}
\foo a b c

并以 a、b 和 c（而不是它们之间的空格）作为三个参数。

通常的解决方案是使用\futurelet（或如下所示\afterassignment和\let），但这取决于您想要做什么。

您的 catcode 发生变化，例如

\catcode`\ \active

没有效果，因为空格已经在\scan宏的参数中被标记了。

10，10，

即使你修复了扫描仪，你也不应该期望连续的 10，因为输入文件中任何数量的连续空格都被标记为单个 catcode 10 标记

\documentclass{article}

\def\scan#1{\xscan#1\relax}
\def\xscan{\afterassignment\xxscan\let\tmp= }
\def\xxscan{%
\ifx\tmp\relax\else
\ifcat\tmp\space10 \else
\ifcat\tmp a11 \else
\ifcat\tmp 112 \else%...
\fi\fi\fi
\expandafter\xscan
\fi}



\begin{document}

\scan{  mac::exception  ==  }

\end{document}