自定义 \if 命令来检查多个条件

Question 1

一行代码expl3：

\documentclass{article}
\usepackage{xparse}

\ExplSyntaxOn
% this assumes that \classversion contains the version

\NewDocumentCommand{\ifVersion}{mmO{}}
 {% #1 is a list of items of the form {year,...}
  % #2 is the code to execute in case of a match
  % #3 (optional) is the code to use in case of no match
  \str_if_in:nVTF { #1 } \classversion { #2 } { #3 }
 }
\prg_generate_conditional_variant:Nnn \str_if_in:nn { nV } { T, F, TF }
\ExplSyntaxOff

\def\classversion{2018} % emulate what the class does

\begin{document}

\ifVersion{2018}{Version 2018}[Not version 2018]

\ifVersion{2017,2018}{This is 2017 or 2018}

\ifVersion{2016}{Nothing} $\leftarrow$ nothing

\ifVersion{2016}{Nothing}[Not 2016]

\ifVersion{2016,2017}{Nothing} $\leftarrow$ nothing

\end{document}

Answer

一行代码expl3：

\documentclass{article}
\usepackage{xparse}

\ExplSyntaxOn
% this assumes that \classversion contains the version

\NewDocumentCommand{\ifVersion}{mmO{}}
 {% #1 is a list of items of the form {year,...}
  % #2 is the code to execute in case of a match
  % #3 (optional) is the code to use in case of no match
  \str_if_in:nVTF { #1 } \classversion { #2 } { #3 }
 }
\prg_generate_conditional_variant:Nnn \str_if_in:nn { nV } { T, F, TF }
\ExplSyntaxOff

\def\classversion{2018} % emulate what the class does

\begin{document}

\ifVersion{2018}{Version 2018}[Not version 2018]

\ifVersion{2017,2018}{This is 2017 or 2018}

\ifVersion{2016}{Nothing} $\leftarrow$ nothing

\ifVersion{2016}{Nothing}[Not 2016]

\ifVersion{2016,2017}{Nothing} $\leftarrow$ nothing

\end{document}

Question 2

expl3使用with 的简单实现\if ... \fi：

\documentclass{article}
\usepackage{expl3,xparse}
\ExplSyntaxOn
\str_new:N\g_my_version_str
\NewDocumentCommand\setVersion{ m }{
  \str_gset:Nn \g_my_version_str { #1 }
}
\NewDocumentCommand\ifVersion{ m }{
  \clist_if_in:nVTF { #1 } {\g_my_version_str} {\iftrue} {\iffalse}
}
\ExplSyntaxOff
\begin{document}
\setVersion{2018}
\ifVersion{2017, 2018}
+1\\
\fi
\ifVersion{2017, 2015}
+2\\
\fi
\end{document}

这会导致嵌套条件出现问题，因为 TeX 不将其\ifVersion视为\if命令，因此\else/\fi解析在未评估的上下文中不同步。

相反，最好将条件命令作为参数传递：

\documentclass{article}
\usepackage{expl3,xparse}
\ExplSyntaxOn
\str_new:N\g_my_version_str
\NewDocumentCommand\setVersion{ m }{
  \str_gset:Nn \g_my_version_str { #1 }
}
\NewDocumentCommand\ifVersion{ m }{
  \clist_if_in:nVTF { #1 } {\g_my_version_str}
}
\ExplSyntaxOff
\begin{document}
\setVersion{2018}
\ifVersion{2017, 2018}{+1}{Not +1}
\ifVersion{2017, 2015}{+2}{Not +2}
\end{document}

Answer

expl3使用with 的简单实现\if ... \fi：

\documentclass{article}
\usepackage{expl3,xparse}
\ExplSyntaxOn
\str_new:N\g_my_version_str
\NewDocumentCommand\setVersion{ m }{
  \str_gset:Nn \g_my_version_str { #1 }
}
\NewDocumentCommand\ifVersion{ m }{
  \clist_if_in:nVTF { #1 } {\g_my_version_str} {\iftrue} {\iffalse}
}
\ExplSyntaxOff
\begin{document}
\setVersion{2018}
\ifVersion{2017, 2018}
+1\\
\fi
\ifVersion{2017, 2015}
+2\\
\fi
\end{document}

这会导致嵌套条件出现问题，因为 TeX 不将其\ifVersion视为\if命令，因此\else/\fi解析在未评估的上下文中不同步。

相反，最好将条件命令作为参数传递：

\documentclass{article}
\usepackage{expl3,xparse}
\ExplSyntaxOn
\str_new:N\g_my_version_str
\NewDocumentCommand\setVersion{ m }{
  \str_gset:Nn \g_my_version_str { #1 }
}
\NewDocumentCommand\ifVersion{ m }{
  \clist_if_in:nVTF { #1 } {\g_my_version_str}
}
\ExplSyntaxOff
\begin{document}
\setVersion{2018}
\ifVersion{2017, 2018}{+1}{Not +1}
\ifVersion{2017, 2015}{+2}{Not +2}
\end{document}

Question 3

不用任何包你也可以做到这一点：

\documentclass{article}

\makeatletter
\newcommand{\setVersion}[1]{\def\fire@version{#1}}

\setVersion{2018-06-08}

\newcommand{\ifVersion}[1]{\ifnum\numexpr#1>0
    \expandafter\@firstoftwo
  \else
    \expandafter\@secondoftwo
  \fi
}

\newcommand\IS[1]{%
  \if0\expandafter\pdfstrcmp\expandafter{\fire@version}{#1}%
    \expandafter1%
  \else
    \expandafter0%
  \fi}

\newcommand\ISNOT[1]{%
  \if0\expandafter\pdfstrcmp\expandafter{\fire@version}{#1}%
    \expandafter0%
  \else
    \expandafter1%
  \fi}

\newcommand\AND[2]{(#1*#2)}

\newcommand\OR[2]{(#1+#2-#1*#2)}

\newcommand\NOT[1]{(1-#1)}

\makeatother

\begin{document}

\ifVersion
{\AND{\OR{\OR{\IS{v1}}{\IS{v2}}}{\IS{2018-06-08}}}{\ISNOT{2017-05-11}}}
{YES}
{NO}
% YES

\ifVersion
{\OR{\OR{\OR{\IS{v1}}{\IS{v2}}}{\IS{2018-06-08}}}{\IS{2017-05-11}}}
{YES}
{NO}
% YES

\ifVersion
{\AND{\OR{\OR{\IS{v1}}{\IS{v2}}}{\IS{2018-06-08}}}{\IS{2017-05-11}}}
{YES}
{NO}
% NO

\end{document}

使用上述解决方案是\pdfstrcmp因为我不想假设版本号仅仅是数字。

以上内容可以嵌套，没有问题。

现在，为了更方便的中缀表示法，你可以使用 xintexpr它提供了\xintifboolexpr和函数以及bool()。togl()查看文档。这将允许您bool()在任意复杂的逻辑表达式中组合（与）TeX 条件。

Answer