为了娱乐

Question 1

我通过测量当前样式中的分数\mathpalette。然后我添加一个，\vrule其高度与数学轴（\fontdimen22系列 2 中的当前字体）加上默认规则厚度的一半（\fontdime8系列 3 中的当前字体）一样高，深度与分数一样深，宽度为默认规则厚度。

需要一些负空间，也就是-\nulldelimiterspace，我在构造之后将其添加回来。

为了留出一些空间，我在分母的两边都加了一些细小的空间。

\documentclass{article}
\usepackage{amsmath}
\usepackage{unicode-math} % comment out for pdflatex

\makeatletter
\newcommand{\funnyfrac}[2]{{\mathpalette\funny@frac{{#1}{#2}}}}
\newcommand{\funny@frac}[2]{\funny@@frac#1#2}% trick for passing three args to \mathpalette
\newcommand{\funny@@frac}[3]{%
  \begingroup
  \sbox\z@{$\m@th#1\frac{#2}{\,#3\,}$}%
  \usebox\z@
  \kern-\nulldelimiterspace
  \funny@fractionrule{#1}%
  \kern\nulldelimiterspace
  \endgroup
}
\newcommand{\math@param}[3]{%
  \fontdimen#3
  \ifx#1\displaystyle\textfont#2
  \else\ifx#1\textstyle\textfont#2
  \else\ifx#1\scriptstyle\scriptfont#2
  \else\scriptscriptfont#2 \fi\fi\fi
}
\@ifpackageloaded{unicode-math}{%
  \usepackage{ifluatex}
  \ifluatex
    \newcommand{\funny@fractionrule}[1]{%
      \vrule height \dimexpr\Umathaxis#1+0.5\Umathfractionrule#1\relax
             depth \dp\z@
             width \Umathfractionrule#1\relax
    }
  \else
    \usepackage{xfp}
    \newcommand{\funny@fractionrule}[1]{%
      \sbox\tw@{$\textstyle x$}\sbox\@tempboxa{$#1x$}%
      \vrule height \fpeval{\ht\@tempboxa/\ht\tw@}%
                    \dimexpr\fontdimen22\textfont2+0.5\fontdimen8\textfont3\relax
             depth \dp\z@
             width \fpeval{\ht\@tempboxa/\ht\tw@}\fontdimen8\textfont3
    }
  \fi
}{% no unicode-math
  \newcommand{\funny@fractionrule}[1]{%
    \vrule height \dimexpr\math@param{#1}{2}{22}+0.5\math@param{#1}{3}{8}\relax
           depth \dp\z@
           width \math@param{#1}{3}{8} % default rule width
  }
}
\makeatother

\begin{document}

$\displaystyle\funnyfrac{a}{b}$
$\textstyle\funnyfrac{a}{b}$
$\scriptstyle\funnyfrac{a}{b}$
$\scriptscriptstyle\funnyfrac{a}{b}$
$\displaystyle\funnyfrac{a}{\dfrac{1}{2}}$
$\funnyfrac{a+b}{c}+\funnyfrac{a}{b+c}$

\end{document}

Answer

我通过测量当前样式中的分数\mathpalette。然后我添加一个，\vrule其高度与数学轴（\fontdimen22系列 2 中的当前字体）加上默认规则厚度的一半（\fontdime8系列 3 中的当前字体）一样高，深度与分数一样深，宽度为默认规则厚度。

需要一些负空间，也就是-\nulldelimiterspace，我在构造之后将其添加回来。

为了留出一些空间，我在分母的两边都加了一些细小的空间。

\documentclass{article}
\usepackage{amsmath}
\usepackage{unicode-math} % comment out for pdflatex

\makeatletter
\newcommand{\funnyfrac}[2]{{\mathpalette\funny@frac{{#1}{#2}}}}
\newcommand{\funny@frac}[2]{\funny@@frac#1#2}% trick for passing three args to \mathpalette
\newcommand{\funny@@frac}[3]{%
  \begingroup
  \sbox\z@{$\m@th#1\frac{#2}{\,#3\,}$}%
  \usebox\z@
  \kern-\nulldelimiterspace
  \funny@fractionrule{#1}%
  \kern\nulldelimiterspace
  \endgroup
}
\newcommand{\math@param}[3]{%
  \fontdimen#3
  \ifx#1\displaystyle\textfont#2
  \else\ifx#1\textstyle\textfont#2
  \else\ifx#1\scriptstyle\scriptfont#2
  \else\scriptscriptfont#2 \fi\fi\fi
}
\@ifpackageloaded{unicode-math}{%
  \usepackage{ifluatex}
  \ifluatex
    \newcommand{\funny@fractionrule}[1]{%
      \vrule height \dimexpr\Umathaxis#1+0.5\Umathfractionrule#1\relax
             depth \dp\z@
             width \Umathfractionrule#1\relax
    }
  \else
    \usepackage{xfp}
    \newcommand{\funny@fractionrule}[1]{%
      \sbox\tw@{$\textstyle x$}\sbox\@tempboxa{$#1x$}%
      \vrule height \fpeval{\ht\@tempboxa/\ht\tw@}%
                    \dimexpr\fontdimen22\textfont2+0.5\fontdimen8\textfont3\relax
             depth \dp\z@
             width \fpeval{\ht\@tempboxa/\ht\tw@}\fontdimen8\textfont3
    }
  \fi
}{% no unicode-math
  \newcommand{\funny@fractionrule}[1]{%
    \vrule height \dimexpr\math@param{#1}{2}{22}+0.5\math@param{#1}{3}{8}\relax
           depth \dp\z@
           width \math@param{#1}{3}{8} % default rule width
  }
}
\makeatother

\begin{document}

$\displaystyle\funnyfrac{a}{b}$
$\textstyle\funnyfrac{a}{b}$
$\scriptstyle\funnyfrac{a}{b}$
$\scriptscriptstyle\funnyfrac{a}{b}$
$\displaystyle\funnyfrac{a}{\dfrac{1}{2}}$
$\funnyfrac{a+b}{c}+\funnyfrac{a}{b+c}$

\end{document}

Question 2

下面的代码应该可以为您提供规则的正确深度。

在第一个版本中，我假设分数规则宽度等于 0.4pt（默认规则宽度）。感谢egreg 的回答，我用一个扩展为\fontdimen8适当数学字体的宏（\textfont3，\scriptfont3或\scriptscriptfont3，取决于当前的数学样式）替换了这个 0.4pt。

语法非常简单：只需使用\strange或\strangeii代替\frac。

注意：我添加\Bigg分隔符并不是因为它们看起来不错，而是为了显示垂直线与分数分母一样深，而不是与整个公式一样深——如果删除替换文本和中的外括号，就会出现这种情况\strange（\strangeii这些括号会创建一个子公式与分数一样高、一样深）。

\documentclass{article}
\usepackage{xparse}

\makeatletter

% Small amount of expl3 code for the DRY principle
\ExplSyntaxOn

\cs_new_protected:Npn \__michael_mathchoice:nnnn #1#2#3#4
  { \mathchoice {#1} {#2} {#3} {#4} }

\cs_generate_variant:Nn \__michael_mathchoice:nnnn { oooo }

% Expand to a \fontdimen parameter of a math font
%
% #1: 'text', 'script' or 'scriptscript' (for \textfont, \scriptfont or
%     \scriptscriptfont, respectively)
% #2: font family (0-16)
% #3: number of the font parameter (cf. TeXbook p. 447)
\cs_new:Npn \__michael_math_param:nnn #1#2#3
  { \fontdimen #3 \use:c { #1font } #2 }

% Default rule width \__michael_math_param:nnn {#1} {3} {8} based on a hint
% from egreg's answer (<https://tex.stackexchange.com/a/499972/73317>).
\cs_new_protected:Npn \__michael_small_rule:n #1
  {
    \vrule
      width  \dim_eval:n { \__michael_math_param:nnn {#1} {3} {8} }
      height \dim_eval:n { \__michael_math_param:nnn {#1} {2} {22} +
                           0.5\__michael_math_param:nnn {#1} {3} {8} }
    \relax
  }

% Generate the vertical rule to be used on the right of the fraction
% in the appropriate style.
\NewDocumentCommand \michaelsmallrule { }
  {
    \__michael_mathchoice:oooo
      { \__michael_small_rule:n { text } }
      { \__michael_small_rule:n { text } }
      { \__michael_small_rule:n { script } }
      { \__michael_small_rule:n { scriptscript } }
  }

\ExplSyntaxOff

\newcommand*{\strangeii}[2]{% No need for the % here: we are in math mode
  { \frac{#1}{#2} \michaelsmallrule }
}

% See <https://tex.stackexchange.com/a/233033/73317> and TeXbook p. 150
\newcommand*{\strange}[2]{% with correction for horizontal space
  { \frac{#1}{#2} \kern-\nulldelimiterspace \michaelsmallrule }
}

\newcommand*{\mytest}[1]{%
  \par
  In text style: $\Biggl(2 + #1{x+1}{(2y-8)^2} \Biggr)$; in subscripts and
  subsubscripts:
  $\Gamma_{ #1{a+1}{1+#1{x}{y}^{#1{\alpha}{\beta}}} }$; finally, in a display formula:
  \[ \Biggl( 2 + #1{x+1}{(2y-8)^2} \Biggr). \]
}

\makeatother

\begin{document}

\section*{With \texttt{\string\strange}}

\mytest{\strange}

\section*{With \texttt{\string\strangeii}}

\mytest{\strangeii}

\end{document}

放大\strange在\scriptstyle和中显示的第一个表达式\scriptscriptstyle：

为了娱乐

可以推动DRY 原则代码中还有一点expl3。我上面没有这样做，因为我认为它会让代码更难阅读；但如果你感兴趣的话，你可以看看：

\cs_new_protected:Npn \__michael_small_rule_aux:n #1
  { \__michael_mathchoice:oooo #1 }

\cs_generate_variant:Nn \__michael_small_rule_aux:n { V }

% Generate the little vertical rule from middle to top of the fraction rule
% in the appropriate style.
\NewDocumentCommand \michaelsmallrule { }
  {
    % Prepare the argument list for the four styles; store it in \l_tmpa_tl.
    \tl_clear:N \l_tmpa_tl
    \clist_map_inline:nn { text, text, script, scriptscript }
      {
        \tl_put_right:Nn \l_tmpa_tl { { \__michael_small_rule:n {##1} } }
      }

    % Expand \l_tmpa_tl to construct the four arguments (they correspond to
    % the arguments of \mathchoice, except that one expansion step will be
    % done in each argument before it is fed to \matchoice)
    \__michael_small_rule_aux:V \l_tmpa_tl
  }

\michaelsmallrule这可以替换上面给出的完整代码示例中的定义。

Answer

下面的代码应该可以为您提供规则的正确深度。

在第一个版本中，我假设分数规则宽度等于 0.4pt（默认规则宽度）。感谢egreg 的回答，我用一个扩展为\fontdimen8适当数学字体的宏（\textfont3，\scriptfont3或\scriptscriptfont3，取决于当前的数学样式）替换了这个 0.4pt。

语法非常简单：只需使用\strange或\strangeii代替\frac。

注意：我添加\Bigg分隔符并不是因为它们看起来不错，而是为了显示垂直线与分数分母一样深，而不是与整个公式一样深——如果删除替换文本和中的外括号，就会出现这种情况\strange（\strangeii这些括号会创建一个子公式与分数一样高、一样深）。

\documentclass{article}
\usepackage{xparse}

\makeatletter

% Small amount of expl3 code for the DRY principle
\ExplSyntaxOn

\cs_new_protected:Npn \__michael_mathchoice:nnnn #1#2#3#4
  { \mathchoice {#1} {#2} {#3} {#4} }

\cs_generate_variant:Nn \__michael_mathchoice:nnnn { oooo }

% Expand to a \fontdimen parameter of a math font
%
% #1: 'text', 'script' or 'scriptscript' (for \textfont, \scriptfont or
%     \scriptscriptfont, respectively)
% #2: font family (0-16)
% #3: number of the font parameter (cf. TeXbook p. 447)
\cs_new:Npn \__michael_math_param:nnn #1#2#3
  { \fontdimen #3 \use:c { #1font } #2 }

% Default rule width \__michael_math_param:nnn {#1} {3} {8} based on a hint
% from egreg's answer (<https://tex.stackexchange.com/a/499972/73317>).
\cs_new_protected:Npn \__michael_small_rule:n #1
  {
    \vrule
      width  \dim_eval:n { \__michael_math_param:nnn {#1} {3} {8} }
      height \dim_eval:n { \__michael_math_param:nnn {#1} {2} {22} +
                           0.5\__michael_math_param:nnn {#1} {3} {8} }
    \relax
  }

% Generate the vertical rule to be used on the right of the fraction
% in the appropriate style.
\NewDocumentCommand \michaelsmallrule { }
  {
    \__michael_mathchoice:oooo
      { \__michael_small_rule:n { text } }
      { \__michael_small_rule:n { text } }
      { \__michael_small_rule:n { script } }
      { \__michael_small_rule:n { scriptscript } }
  }

\ExplSyntaxOff

\newcommand*{\strangeii}[2]{% No need for the % here: we are in math mode
  { \frac{#1}{#2} \michaelsmallrule }
}

% See <https://tex.stackexchange.com/a/233033/73317> and TeXbook p. 150
\newcommand*{\strange}[2]{% with correction for horizontal space
  { \frac{#1}{#2} \kern-\nulldelimiterspace \michaelsmallrule }
}

\newcommand*{\mytest}[1]{%
  \par
  In text style: $\Biggl(2 + #1{x+1}{(2y-8)^2} \Biggr)$; in subscripts and
  subsubscripts:
  $\Gamma_{ #1{a+1}{1+#1{x}{y}^{#1{\alpha}{\beta}}} }$; finally, in a display formula:
  \[ \Biggl( 2 + #1{x+1}{(2y-8)^2} \Biggr). \]
}

\makeatother

\begin{document}

\section*{With \texttt{\string\strange}}

\mytest{\strange}

\section*{With \texttt{\string\strangeii}}

\mytest{\strangeii}

\end{document}

放大\strange在\scriptstyle和中显示的第一个表达式\scriptscriptstyle：

为了娱乐

可以推动DRY 原则代码中还有一点expl3。我上面没有这样做，因为我认为它会让代码更难阅读；但如果你感兴趣的话，你可以看看：

\cs_new_protected:Npn \__michael_small_rule_aux:n #1
  { \__michael_mathchoice:oooo #1 }

\cs_generate_variant:Nn \__michael_small_rule_aux:n { V }

% Generate the little vertical rule from middle to top of the fraction rule
% in the appropriate style.
\NewDocumentCommand \michaelsmallrule { }
  {
    % Prepare the argument list for the four styles; store it in \l_tmpa_tl.
    \tl_clear:N \l_tmpa_tl
    \clist_map_inline:nn { text, text, script, scriptscript }
      {
        \tl_put_right:Nn \l_tmpa_tl { { \__michael_small_rule:n {##1} } }
      }

    % Expand \l_tmpa_tl to construct the four arguments (they correspond to
    % the arguments of \mathchoice, except that one expansion step will be
    % done in each argument before it is fed to \matchoice)
    \__michael_small_rule_aux:V \l_tmpa_tl
  }

\michaelsmallrule这可以替换上面给出的完整代码示例中的定义。

Question 3

像这样？

\documentclass{article}

\begin{document}

\[ \frac{A }{B\smash{\rule{0.4pt}{2.2ex}}} \quad\frac{A}{B}\]%

\end{document}

Answer

像这样？

\documentclass{article}

\begin{document}

\[ \frac{A }{B\smash{\rule{0.4pt}{2.2ex}}} \quad\frac{A}{B}\]%

\end{document}

Question 4

只是为了好玩。

\documentclass{article}

\usepackage{tikz,amsmath}
\newcommand{\mytikzmark}[2]{%
  \tikz[remember picture,inner sep=-1pt,outer sep=0pt,baseline,anchor=base] 
    \node (#1) {\ensuremath{#2}};}

\begin{document}

\[ q 
  = \mytikzmark{n}{\dfrac{{Q_l}}{2}} 
  \]
\begin{tikzpicture}[overlay,remember picture]
  \draw (n.-10)  --++(-90:0.35);

\end{tikzpicture}
\end{document}

Answer

只是为了好玩。

\documentclass{article}

\usepackage{tikz,amsmath}
\newcommand{\mytikzmark}[2]{%
  \tikz[remember picture,inner sep=-1pt,outer sep=0pt,baseline,anchor=base] 
    \node (#1) {\ensuremath{#2}};}

\begin{document}

\[ q 
  = \mytikzmark{n}{\dfrac{{Q_l}}{2}} 
  \]
\begin{tikzpicture}[overlay,remember picture]
  \draw (n.-10)  --++(-90:0.35);

\end{tikzpicture}
\end{document}

为了娱乐

答案1

答案2

为了娱乐

答案3

答案4

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