1

How to produce an arrow under an interval in order to indicate that the two elements may have to be reversed?

For instance I would like to typeset [x, y] with a double-headed arrow between x and y.

Here is a sketch of the desire output:

sketch

I am using AMS packages.

2

Since this is tagged tikz-arrows, I am wondering if you are looking for something like this.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{tikzmark,arrows.meta,bending}
\begin{document}
\[ [\tikzmarknode{x}{x},\tikzmarknode{y}{y}]\qquad 
[\tikzmarknode{Sn}{S_n},\tikzmarknode{Sn+1}{S_{n+1}}]
\begin{tikzpicture}[overlay,remember picture,>={Stealth[bend]}]
\draw[<->] (x.south|-y.south) to[out=-70,in=-110] (y.south);
\draw[<->] (Sn.south|-Sn+1.south) to[out=-70,in=-110] (Sn+1.south);
\end{tikzpicture}\]
\end{document}

enter image description here

| improve this answer | |
  • It is a bit verbose but it does the job – user152057 Dec 27 '19 at 12:23
3

Here are some possibilities with the curved arrows of mathabx, without having to load the package, and \underset/ _overset or with stackengine:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{mathtools, amssymb}
\usepackage[usestackEOL]{stackengine} 

\DeclareFontFamily{U}{mathb}{\hyphenchar\font45}
\DeclareFontShape{U}{mathb}{m}{n}{%
 <-6> mathb5 
 <6-7> mathb6 
 <7-8> mathb7 
 <8-9> mathb8 
 <9-10> mathb9 
 <10-12> mathb10 
 <12-> mathb12 }{}
\DeclareSymbolFont{mathb}{U}{mathb}{m}{n}

\DeclareMathSymbol{\abxcurvearrowleft}{\mathrel}{mathb}{"F0}
\DeclareMathSymbol{\abxcurvearrowright}{\mathrel}{mathb}{"F1}
\DeclareMathSymbol{\curvearrowleftright}{\mathrel}{mathb}{"F2}
\DeclareMathSymbol{\curvearrowbotleft}{\mathrel}{mathb}{"F3}
\DeclareMathSymbol{\curvearrowbotright}{\mathrel}{mathb}{"F4}
\DeclareMathSymbol{\curvearrowbotleftright}{\mathrel}{mathb}{"F5}


\begin{document}

\[ [ \underset{\curvearrowbotleftright}{a, b}] \qquad [ \overset{\curvearrowleftright}{a, b}]\qquad [ \overset{\abxcurvearrowleft}{ \underset{\curvearrowbotright}{a, b}}] \]%

\setstackgap{S}{1pt}%
\setstackgap{L}{7pt}
\[\stackMath [ \Shortunderstack{a, b\\\curvearrowbotleftright}] \qquad [ \Shortstack{\curvearrowleftright\\a, \vphantom{i}\smash[t]{b}}]\qquad [ \Vectorstack{\abxcurvearrowleft\\ a, b \\ \curvearrowbotright}]\]%

\end{document} 

enter image description here

| improve this answer | |
2

Using \underset from amsmath and \longleftrightarrow:

\documentclass[border=3.14]{standalone}

\usepackage[]{amsmath}

\begin{document}
$\underset{\longleftrightarrow}{[x,y]}$
\end{document}

enter image description here

If you think that this arrow is too long, you might use the normal \leftrightarrow:


\documentclass[border=3.14]{standalone}

\usepackage[]{amsmath}

\begin{document}
$\underset{\leftrightarrow}{[x,y]}$
\end{document}

enter image description here

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy