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修复 keyval 问题

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修复 keyval 问题

这是我第一次尝试宏keyval。我有一个更复杂的宏，可以归结为下面给出的 MWE。这个想法是将一个段落排版为多列，其中列数是一个可选的命名参数。当我指定列数时，它就可以工作，但是当没有指定任何选项时，我希望默认为一列。

\documentclass{article}

\usepackage{keyval}
\usepackage{lipsum}
\usepackage{multicol}

\makeatletter

\def\printparagraph{\@ifnextchar[\@printparagraph{\@printparagraph[]}}
\def\@printparagraph[#1]{{\setkeys{pp}{#1}}}
\define@key{pp}{columns}{\begin{multicols}{#1}\lipsum[1]\end{multicols}}

\makeatother

\begin{document}

\printparagraph % this doesn't work, doesn't print anything!
\printparagraph[columns=2] % this works
\printparagraph[columns=3] % this works

\end{document}

答案1

您只需要在默认情况下打印虚拟文本：

\documentclass{article}

\usepackage{keyval}
\usepackage{lipsum}
\usepackage{multicol}

\makeatletter

\def\printparagraph{\@ifnextchar[\@printparagraph{\lipsum}}
\def\@printparagraph[#1]{{\setkeys{pp}{#1}}}
\define@key{pp}{columns}{\begin{multicols}{#1}\lipsum[1]\end{multicols}}

\makeatother

\begin{document}

\printparagraph % 
\printparagraph[columns=2] % this works
\printparagraph[columns=3] % this works

\end{document}

答案2

\begin{multicols{1}不起作用，但除此之外：我不会将多列放在键定义中，而只使用它来存储值。然后很容易设置默认值（我也会使用 l3keys 而不是 keyval，但这是另一个问题）：

\documentclass{article}

\usepackage{keyval}
\usepackage{lipsum}
\usepackage{multicol}

\makeatletter
\newcount\my@columns@cnt
\def\printparagraph{\@ifnextchar[\@printparagraph{\@printparagraph[]}}

\def\@printparagraph[#1]{{%
 \setkeys{pp}{columns,#1}%
 \ifnum\my@columns@cnt=1 
  \expandafter\@firstoftwo
 \else 
  \expandafter\@secondoftwo
 \fi
 {\lipsum[1]}
 {\begin{multicols}{\the\my@columns@cnt}\lipsum[1]\end{multicols}}}}

\define@key{pp}{columns}[1]{\my@columns@cnt=#1\relax}

\makeatother

\begin{document}

\printparagraph % this doesn't work, doesn't print anything!
\printparagraph[columns=2] % this works
\printparagraph[columns=3] % this works

\end{document}

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