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\tl_case:Nn(TF) 和 \str_case:nn(TF) 的良好示例

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\tl_case:Nn(TF) 和 \str_case:nn(TF) 的良好示例

在学习 时expl3，我很难使用\str_case:nn(TF)和\tl_case:Nn(TF)。我在网上找不到好的例子。（例如，unravel对我来说太复杂了。）你能提供独立、简洁、实用的应用示例\tl_case:Nn(TF)吗\str_case:nn(TF)？让我们来解决

  1. \tl_case:NnTF
  2. \str_case:nnTF
  3. \str_case_e:nnTF

首先。我从http://mirrors.ctan.org/macros/latex/contrib/l3kernel/interface3.pdf。如果您希望提供其他后缀的示例，例如：cnTF、:Nn 等，请随意。

答案1

\str_case:nnTF这只是应用、\str_case_e:nn和的演示\tl_case:nnTF。

等情况:cnTF已在问题的评论中解释过。

\str_case_e和之间的区别\str_case在于参数的扩展。\tl..和之间的区别\str..在于，对于字符串，所有字符的 catcode 都相等 (12)，除了空格字符，其代码仍为 10，而在标记列表中，catcode 会保留。

这些\foo:nnTF版本只是将条件分支输入到输入流中——可以使用匹配的括号{foobar}{...}进行进一步处理或设置（或“排版”）或将其转移到 TF 分支。

我个人\foo:nn只使用并且不记得我\foo:nnTF到目前为止需要什么，但是这当然取决于实际的用例。

\documentclass{article}

\usepackage{expl3}

\ExplSyntaxOn

\newcommand{\strcase}[1]{%
  \str_case:nn {#1} {
    {TeX} {\use:c{#1}\space is\space the\space predecessor\space of\space \LaTeX}
    {LaTeX} {\use:c{#1}\space is\space the\space successor\space of\space \TeX}
  }
}

\newcommand{\strcasetf}[3]{%
  \str_case:nnTF {#1} {
    {TeX} {\use:c{#1}\space is\space the\space predecessor\space of\space \LaTeX}
    {LaTeX} {\use:c{#1}\space is\space the\space successor\space of\space \TeX}
    {Word} {#1\space is\space a\space 'typesetter'}
  }{
    \space#2
  }{
    \space#3
  }
}

\newcommand{\genericstrcase}[3]{%
  \str_case:nn {#3} {
    {#1} {It was the first argument}
    {#2} {It was the second argument}
    {Other} {#1 it was 'other'}
  }
}


\newcommand{\strcasextf}[3]{%
  \str_case_e:nnTF {#1} {
    {TeX} {\use:c{#1}\space is\space the\space predecessor\space of\space \LaTeX}
    {LaTeX} {\use:c{#1}\space is\space the\space successor\space of\space \TeX}
    {Word} {#1\space is\space a\space 'typesetter'}
  }{
    \space#2
  }{
    \space#3
  }
}

\tl_new:N \l_tl_one
\tl_new:N \l_tl_two

\newcommand{\tlcase}[3]{%
  \tl_set:Nn \l_tl_one {#1}
  \tl_set:Nn \l_tl_two {#2}

\tl_set:Nn \l_tmpa_tl {#3}

\tl_case:Nn \l_tmpa_tl {
  {\l_tl_one} {Yes,\space it\space was\space #1}
  {\l_tl_two}  {Yes,\space it\space was\space #2}
}
}

\ExplSyntaxOff

\newcommand{\LaTeXStr}{LaTeX}
\newcommand{\WordPressString}{WordPress}
\newcommand{\WordString}{Word}


\begin{document}

\strcase{TeX}

\strcase{LaTeX}

\strcasetf{LaTeX}{-- the strings match}{-- the strings does not match!}

\strcasetf{Word}{-- the strings match}{-- the strings does not match!}

\strcasetf{WordPress}{-- the strings match}{-- the strings does not match!}

\textbf{Compare}

\strcasetf{\LaTeXStr}{-- the strings match}{-- the strings does not match!}

\strcasextf{\LaTeXStr}{-- the strings match}{-- the strings does not match!}

\tlcase{LaTeX}{TeX}{LaTeX}
\tlcase{LaTeX}{TeX}{\LaTeX} % Does nothing, since \LaTeX is not expanded

\textbf{Comparing command tokens}

\tlcase{\LaTeX}{TeX}{\LaTeX}% Compares again

\tlcase{LaTeX is very nice}{TeX}{LaTeX is very nice} 
\tlcase{TeX is nice}{TeX is not outdated}{TeX is very nice} % Does not match

\textbf{Comparing strings}

\genericstrcase{LaTeX}{TeX}{LaTeX}

\genericstrcase{ #LaTeX}{ #TeX}{ #TeX}

\genericstrcase{\LaTeX}{TeX}{\LaTeX}

\end{document}

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