双弯箭头

Question

我发现amssymb有双箭头的代码是$\rightleftarrows$。

我的问题是：我们有命令吗对于双曲线箭头，上面的是向下凹的（箭头从左到右），下面的是向上凹的（箭头从右到左）？

如果我们没有，我们可以制作它并将其用作单一代码吗？

下面是我正在寻找的那种弯曲箭头的图片。

Answer 1

在我看来，下面的内容看起来还不错：

\documentclass[]{article}

\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{tikz}
\usetikzlibrary{arrows}

\newcommand*\curvedrightleft{%
  \mathrel{%
    \begin{tikzpicture}[scale=0.5]%
      \draw[->] (0,0.05) to [out=30,in=150] (1,0.05);%
      \draw[->] (1,-0.05) to [out=-150,in=-30] (0,-0.05);%
    \end{tikzpicture}%
  }%
}

\begin{document}
$A \curvedrightleft B$
\end{document}

Answer 2

中有匹配的符号mathabx，只需将它们堆叠在一起即可。它可以轻松制作成各种尺寸的美观图案。

\documentclass{article}
\usepackage{amsmath}

\DeclareFontFamily{U}{mathb}{\hyphenchar\font45}
\DeclareFontShape{U}{mathb}{m}{n}{
      <5> <6> <7> <8> <9> <10> gen * mathb
      <10.95> mathb10 <12> <14.4> <17.28> <20.74> <24.88> mathb12
      }{}
\DeclareSymbolFont{mathb}{U}{mathb}{m}{n}
\DeclareFontSubstitution{U}{mathb}{m}{n}

\DeclareMathSymbol{\curvearrowleft}    {\mathrel}{mathb}{"F0}
\DeclareMathSymbol{\curvearrowbotright}{\mathrel}{mathb}{"F4}

\makeatletter
\newcommand\curvearrowleftbotright{%
  \mathord{\mathpalette\@curvearrowleftbotright\relax}%
}
\newcommand\@curvearrowleftbotright[2]{%
  \raisebox{.3ex}{$#1\m@th\curvearrowleft$}%
  \llap{\raisebox{-.3ex}{$#1\m@th\curvearrowbotright$}}%
}
\makeatother

\begin{document}

\begin{equation*}
  A \curvearrowleftbotright B_{A \curvearrowleftbotright B_{A \curvearrowleftbotright B}}
\end{equation*}

\begin{equation*}
  \mathcal{K}_3 = V / \curvearrowleftbotright = \{ \bar{B}_1, \bar{B}_2, \dotsc \}
\end{equation*}

\end{document}

Answer 3

这是试图结合 Henri Menke 的答案（自动缩放）和 Skillmon 的答案（Ti 的灵活性）的优点钾z）基本思想就是根据一个参考字符（这里是A）的宽度来缩放图片，并使用\mathchoice。

\documentclass[]{article}

\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{tikz}
\usetikzlibrary{arrows}

\newcommand*\curvedrightleft{%
\ifmmode\mathchoice{\mathrel{%
    \begin{tikzpicture}[scale=height("A")/0.45cm]%
      \draw[->] (0,0.05) to [out=30,in=150] (1,0.05);%
      \draw[->] (1,-0.05) to [out=-150,in=-30] (0,-0.05);%
    \end{tikzpicture}%
  }%
}  
{
    \begin{tikzpicture}[scale=height("A")/0.4cm]%
      \draw[->] (0,0.05) to [out=30,in=150] (1,0.05);%
      \draw[->] (1,-0.05) to [out=-150,in=-30] (0,-0.05);%
    \end{tikzpicture}%
  }%
{\mathrel{%
    \begin{tikzpicture}[scale=height("A")/0.6cm]%
      \draw[->] (0,0.05) to [out=30,in=150] (1,0.05);%
      \draw[->] (1,-0.05) to [out=-150,in=-30] (0,-0.05);%
    \end{tikzpicture}%
  }%
}
{\mathrel{%
    \begin{tikzpicture}[scale=height("A")/0.8cm]%
      \draw[->] (0,0.05) to [out=30,in=150] (1,0.05);%
      \draw[->] (1,-0.05) to [out=-150,in=-30] (0,-0.05);%
    \end{tikzpicture}%
  }%
}
\else
\begin{tikzpicture}[scale=height("A")/0.4cm]%
      \draw[->] (0,0.05) to [out=30,in=150] (1,0.05);%
      \draw[->] (1,-0.05) to [out=-150,in=-30] (0,-0.05);%
\end{tikzpicture}
\fi
}
\begin{document}
$A \curvedrightleft B$ 

$X_{A \curvedrightleft B_{A \curvedrightleft B}}$ 

{\tiny A \curvedrightleft B}

{\Large A \curvedrightleft B}

\end{document}