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\equal 内的 LaTeX3 案例

tag-icon • tag-icon pdftex expl3 ifthenelse
\equal 内的 LaTeX3 案例

我有一个 LaTeX 文档，其中我使用 LaTeX3 语法定义了一个 switch case 命令。我在命令\equal的条件内使用了 case \ifthenelse。但是，我一直得到错误的结果；在我看来，在 中\equal，switch case 无法展开。

我做错了什么？在下面的 MWE 中，我期望“功能是 A:)“但得到了”功能为 B :(“：

\documentclass{book}
\usepackage{xparse}
\usepackage{ifthen}

\ExplSyntaxOn
\newcommand\caseswitch[2]{
  \str_case_e:nn{#1}{#2}
}
\ExplSyntaxOff

\newcommand\mycommand[1]{
  \caseswitch{#1}{
    {A}{Aaa}
    {B}{Bbb}
  }
}

\begin{document}

% expected "Function is A :)" but got "Function is B :("
\ifthenelse{\equal{\mycommand{A}}{Aaa}}{Function is A :)}{Function is B :(}

% another version - does not work too
%\caseswitch{\mycommand{A}}{{Aaa}{Function is A :)}{Bbb}{Function is B :(}}

\end{document}

答案1

一个有趣的案例虚假空间综合症：您正在Aaa与 Aaa （字符串周围有两个空格）进行比较。

\documentclass{book}
\usepackage{xparse}
\usepackage{ifthen}

\ExplSyntaxOn
\newcommand\caseswitch[2]{
  \str_case_e:nn{#1}{#2}
}
\ExplSyntaxOff

\newcommand\mycommand[1]{% <--- HERE
  \caseswitch{#1}{
    {A}{Aaa}
    {B}{Bbb}
  }% <--- HERE
}

\begin{document}

% expected "Function is A :)" but got "Function is B :("
\ifthenelse{\equal{\mycommand{A}}{Aaa}}{Function is A :)}{Function is B :(}

% another version - does not work too
\caseswitch{\mycommand{A}}{{Aaa}{Function is A :)}{Bbb}{Function is B :(}}

\end{document}

在此处输入图片描述

我会用更简单的

\ExplSyntaxOn
\cs_set_eq:NN \caseswitch \str_case_e:nn
\ExplSyntaxOff

以及\ifthenelse我提议的重新实施网站其他地方（请参阅链接了解使用示例）。

\documentclass{book}

\ExplSyntaxOn

%%% Expandable reimplementation of \ifthenelse
\NewExpandableDocumentCommand{\xifthenelse}{mmm}
 {
  \bool_if:nTF { #1 } { #2 } { #3 }
 }

\cs_new_eq:NN \numtest     \int_compare_p:n
\cs_new_eq:NN \oddtest     \int_if_odd_p:n
\cs_new_eq:NN \fptest      \fp_compare_p:n
\cs_new_eq:NN \dimtest     \dim_compare_p:n
\cs_new_eq:NN \deftest     \cs_if_exist_p:N
\cs_new_eq:NN \namedeftest \cs_if_exist_p:c
\cs_new_eq:NN \eqdeftest   \token_if_eq_meaning_p:NN
\cs_new_eq:NN \streqtest   \str_if_eq_p:ee
\cs_new_eq:NN \emptytest   \tl_if_empty_p:n
\cs_new_eq:NN \blanktest   \tl_if_blank_p:n
\cs_new_eq:NN \boolean     \legacy_if_p:n
\cs_new:Npn \modetest #1
 {
  \str_case:nnF { #1 }
   {
    {h}{\mode_if_horizontal_p:}
    {v}{\mode_if_vertical_p:}
    {m}{\mode_if_math_p:}
    {i}{\mode_if_inner_p:}
   }
   {\c_false_bool}
 }
\cs_new:Npn \enginetest #1
 {
  \str_case:nnF { #1 }
   {
    {luatex}{\sys_if_engine_luatex_p:}
    {pdftex}{\sys_if_engine_pdftex_p:}
    {ptex}{\sys_if_engine_ptex_p:}
    {uptex}{\sys_if_engine_uptex_p:}
    {xetex}{\sys_if_engine_xetex_p:}
   }
   {\c_false_bool}
 }

% a utility command
\cs_set_eq:NN \caseswitch \str_case_e:nn

\ExplSyntaxOff

\newcommand\mycommand[1]{%
  \caseswitch{#1}{
    {A}{Aaa}
    {B}{Bbb}
  }%
}

\begin{document}

% expected "Function is A :)" but got "Function is B :("
\xifthenelse{\streqtest{\mycommand{A}}{Aaa}}{Function is A :)}{Function is B :(}

% another version - does not work too
\caseswitch{\mycommand{A}}{{Aaa}{Function is A :)}{Bbb}{Function is B :(}}

\end{document}

答案2

如果您没有使用 Expl3，则需要注意行尾的空格。此外，您实际上并不需要，\ifthenelse特别是如果您已经在使用expl3具有更好控制结构的 Expl3。

\documentclass{book}


\ExplSyntaxOn
\cs_set_eq:NN \caseswitch \str_case_e:nn

\newcommand\mycommand[1]{
  \caseswitch{#1}{
    {A}{Aaa}
    {B}{Bbb}
  }
}
\ExplSyntaxOff

\begin{document}


\caseswitch{\mycommand{A}}{{Aaa}{Function is A :)}{Bbb}{Function is B :(}}

\end{document}

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