双平方根（surd）符号

Question

我想定义一个打印两个相邻的 sqrt 符号的宏。（来自柯西分析书中的符号）。

我得到了一个接近的结果，但间距会根据前面是否有数字而变化。如果前面没有数字，则 sqrt (surd) 符号太近了。

平均能量损失

\documentclass[class=book]{book}
% Run with xelatex

%%% fonts
\usepackage{libertine}

\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}

%%% mathfonts
\usepackage{unicode-math}
\setmathfont{texgyrepagella-math.otf}
\usepackage{microtype}


% "221A is the surd symbol in unicode. \surd is not working, it shows a p
\usepackage{mathtools}
\NewDocumentCommand\dsqrt{o m}{%
  \IfNoValueTF{#1}{%
    \,\mathrlap{\char"221A}\,\char"221A#2%
  }%
  {
    \,\mathrlap{\raisebox{3pt}{$\scriptscriptstyle#1$}}\mathrlap{\char"221A}\,\char"221A#2%
  }
}

\begin{document}

\begin{equation}\label{pre1}
\dsqrt{a} = \pm\sqrt{a}
\end{equation}

\begin{equation}\label{pre1}
2\dsqrt{a} = \pm2\sqrt{a}
\end{equation}

\begin{equation}\label{pre1}
\dsqrt[n]{a} = \pm\sqrt[n]{a}
\end{equation}

\begin{equation}\label{pre1}
2\dsqrt[n]{a} = \pm2\sqrt[n]{a}
\end{equation}

And here is another: inline  $\dsqrt{y} =\pm \sqrt{y}$.

And here is another: inline  $2\dsqrt{y} =\pm 2\sqrt{y}$.

And here is another: inline $\dsqrt[n]{y} =\pm \sqrt[n]{y}$.

And here is another: inline $2\dsqrt[n]{y} =\pm 2\sqrt[n]{y}$.

\end{document}

Answer 1

这是另一次尝试；不幸的是，Unicode 中似乎没有“surd”符号。

\documentclass{book}
% Run with xelatex

%%% fonts
\usepackage{amsmath}
\usepackage{mathtools}
\usepackage{amsfonts}
\usepackage{amssymb}

%%% mathfonts
\usepackage{unicode-math}
\setmainfont{TeX Gyre Pagella}
\setmathfont{texgyrepagella-math.otf}
\usepackage{microtype}

% "221A is the surd symbol in unicode. \surd is not working, it shows a p
\NewDocumentCommand\dsqrt{o m}{%
  \mathop{%
    \IfNoValueTF{#1}
      {\doublesurd}
      {\mathrlap{^{\scriptscriptstyle#1}}\doublesurd}%
  }%
  {}#2
}

\makeatletter
\newcommand{\doublesurd}{\mathpalette\double@surd\relax}
\newcommand{\double@surd}[2]{%
  \ooalign{$\m@th#1\char"221A$\hidewidth\cr$\m@th#1\,\char"221A$\cr}%
}
\makeatother

\begin{document}

\begin{equation}
\dsqrt{a} = \pm\sqrt{a}
\end{equation}

\begin{equation}
2\dsqrt{a} = \pm2\sqrt{a}
\end{equation}

\begin{equation}
\dsqrt[n]{a} = \pm\sqrt[n]{a}
\end{equation}

\begin{equation}
2\dsqrt[n]{a} = \pm2\sqrt[n]{a}
\end{equation}

And here is another: inline  $\dsqrt{y} =\pm \sqrt{y}$.

And here is another: inline  $2\dsqrt{y} =\pm 2\sqrt{y}$.

And here is another: inline $\dsqrt[n]{y} =\pm \sqrt[n]{y}$.

And here is another: inline $2\dsqrt[n]{y} =\pm 2\sqrt[n]{y}$.

\end{document}

Answer 2

这是使用堆栈的版本。但是，它目前尚未设置为遵循较小的数学样式。

\documentclass[class=book]{book}
% Run with xelatex

%%% fonts
\usepackage{libertine}

\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{stackengine}
\stackMath
%%% mathfonts
\usepackage{unicode-math}
\setmathfont{texgyrepagella-math.otf}
\usepackage{microtype}


% "221A is the surd symbol in unicode. \surd is not working, it shows a p
\usepackage{mathtools}
\NewDocumentCommand\dsqrt{o m}{%
  \IfNoValueTF{#1}{%
    \,\stackengine{0pt}{\char"221A}{\,\char"221A#2}{O}{l}{F}{F}{L}%
  }%
  {
    \,\raisebox{3pt}{$\scriptscriptstyle#1$}\mkern-13mu\stackengine{0pt}{\char"221A}{\,\char"221A#2}{O}{l}{F}{F}{L}%
  }
}

\begin{document}

\begin{equation}\label{pre1}
\dsqrt{a} = \pm\sqrt{a}
\end{equation}

\begin{equation}\label{pre1}
2\dsqrt{a} = \pm2\sqrt{a}
\end{equation}

\begin{equation}\label{pre1}
\dsqrt[n]{a} = \pm\sqrt[n]{a}
\end{equation}

\begin{equation}\label{pre1}
2\dsqrt[n]{a} = \pm2\sqrt[n]{a}
\end{equation}

And here is another: inline  $\dsqrt{y} =\pm \sqrt{y}$.

And here is another: inline  $2\dsqrt{y} =\pm 2\sqrt{y}$.

And here is another: inline $\dsqrt[n]{y} =\pm \sqrt[n]{y}$.

And here is another: inline $2\dsqrt[n]{y} =\pm 2\sqrt[n]{y}$.

\end{document}

如果希望无理数与参数大小相匹配（就像 一样\sqrt），那么应该用这个定义来替代：

\NewDocumentCommand\dsqrt{o m}{%
  \IfNoValueTF{#1}{%
    \,\stackengine{0pt}{\sqrt{\vphantom{#2}}}{\,\sqrt{#2}}{O}{l}{F}{F}{L}%
  }%
  {
    \,\raisebox{3pt}{$\scriptscriptstyle#1$}\mkern-13mu\stackengine{0pt}{%
      \sqrt{\vphantom{#2}}}{\,\sqrt{#2}}{O}{l}{F}{F}{L}%
  }
}

x注意与参数的区别y。