在内联数学模式中允许在“，”处换行吗？

Question

在内联数学模式 ( $...$) 中，如果公式太长，LaTeX 将尝试在运算符上将其分解，例如

very long text followed by a very long equation like $a+b+c+d+e+f+g+h+i+j+k+l$ etc

可以表示为

very long text followed
by a very long equation
like a+b+c+d+e+f+g+h+i+
j+k+l etc

但是，如果它们之间用逗号分隔，则不会发生中断，例如

very long text followed by a very long equation like $a,b,c,d,e,f,g,h,i,j,k,l$ etc

会溢出页面，就像

very long text followed
by a very long equation
like a,b,c,d,e,f,g,h,i,j,k,l
etc

如何让 LaTeX 也能在逗号后插入换行符？

Answer 1

如果表达式包含许多逗号，则考虑将其拆分为多个数学表达式，并用逗号分隔。它读起来就像数学表达式列表。这样 TeX 就可以换行了。

若要在逗号后实现换行，可\allowbreak在逗号后和下一个数学符号前插入。如有必要，可在 后留空\allowbreak。

如果你想要一个文档范围的解决方案，你可以重新定义逗号。一个解决方案是按照提示这里将会：

\makeatletter
\def\old@comma{,}
\catcode`\,=13
\def,{%
  \ifmmode%
    \old@comma\discretionary{}{}{}%
  \else%
    \old@comma%
  \fi%
}
\makeatother

Answer 2

你可以看看breqn包，旨在从一般意义上解决这个问题。

Answer 3

这是一个不会使逗号全局生效的解决方案：

\documentclass{article}

\newcommand{\splitatcommas}[1]{%
  \begingroup
  \begingroup\lccode`~=`, \lowercase{\endgroup
    \edef~{\mathchar\the\mathcode`, \penalty0 \noexpand\hspace{0pt plus 1em}}%
  }\mathcode`,="8000 #1%
  \endgroup
}

\begin{document}

\setlength{\lineskiplimit}{2pt}\setlength{\lineskip}{3pt} % for this particular case

$\splitatcommas{
  \frac{1}{2},\frac{3}{5},\frac{8}{13},\frac{21}{34},\frac{55}{89},
  \frac{144}{233},\frac{377}{610},\frac{987}{1597},\frac{2584}{4181},
  \frac{6765}{10946},\frac{17711}{28657},\frac{46368}{75025},
  \frac{121393}{196418},\frac{317811}{514229},\frac{832040}{1346269},
  \frac{2178309}{3524578},\frac{5702887}{9227465},
  \frac{14930352}{24157817},\frac{39088169}{63245986},\frac{102334155}{165580141}
}$

\end{document}

\lineskiplimit和的设置\lineskip适用于论证中需要分数的特殊情况。

允许嵌套的变体：

\documentclass{article}

\newcommand{\splitatcommas}[1]{%
  \begingroup
  \ifnum\mathcode`,="8000
  \else
    \begingroup\lccode`~=`, \lowercase{\endgroup
      \edef~{\mathchar\the\mathcode`, \penalty0 \noexpand\hspace{0pt plus 1em}}%
    }\mathcode`,="8000
  \fi
  #1%
  \endgroup
}

\newcommand{\tuple}[1]{(\splitatcommas{#1})}
\newcommand{\set}[1]{\{\splitatcommas{#1}\}}

\begin{document}

\setlength{\lineskiplimit}{2pt}\setlength{\lineskip}{3pt} % for this particular case

$\splitatcommas{
  \frac{1}{2},\frac{3}{5},\frac{8}{13},\frac{21}{34},\frac{55}{89},
  \frac{144}{233},\frac{377}{610},\frac{987}{1597},\frac{2584}{4181},
  \frac{6765}{10946},\frac{17711}{28657},\frac{46368}{75025},
  \frac{121393}{196418},\frac{317811}{514229},\frac{832040}{1346269},
  \frac{2178309}{3524578},\frac{5702887}{9227465},
  \frac{14930352}{24157817},\frac{39088169}{63245986},\frac{102334155}{165580141}
}$

$\set{
  \tuple{a,b,c,d},\tuple{1,2,3,4,5,6},\tuple{11,22,33,44,55,66,77,88},
  \tuple{a,b,c,d},\tuple{1,2,3,4,5,6},\tuple{11,22,33,44,55,66,77,88},
  \tuple{a,b,c,d},\tuple{1,2,3,4,5,6},\tuple{11,22,33,44,55,66,77,88},
  \tuple{a,b,c,d},\tuple{1,2,3,4,5,6},\tuple{11,22,33,44,55,66,77,88}
}$

\end{document}

Answer 4

在 luatex 中，您有一个不涉及活动字符的新可能性，您可以声明,为 a mathbin(like +)，以便允许换行，然后将 mathord-mathbin 间距设置为零，这样它前面就没有空格，就像标点符号一样：

\documentclass{article}

\begin{document}

$
\mathcode`\,="213B % mathbin
\Umathordbinspacing\textstyle 0mu % no space before
a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,
a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a$
\end{document}