\rightleftarrows in the style of \rightarrowtriangle

Question

Is there a symbol for \rightleftarrows (an arrow to the right above an arrow to the left) but in the style of \rightarrowtriangle (an arrow with a hollow triangular head)?

You can stack the arrows yourself: https://www.ctan.org/pkg/stackengine — samcarter_is_at_topanswers.xyz, Aug 29 '23 at 13:53

Sandy G · Answer 1 · 2023-08-30T15:40:18.947

You can adjust the lengths in the \raisebox commands if you want the symbol at a different height or a different amount of space between. For explanations of \mathchoice and \ooalign, as well as other ways of doing this, you can look at this question and its solutions.

\documentclass{article}
\usepackage[only,rightarrowtriangle,leftarrowtriangle]{stmaryrd}
\newcommand{\leftrightarrowtriangle}{\mathrel{\mathchoice
    {\ooalign{\raisebox{-.2ex}{$\rightarrowtriangle$}\cr\raisebox{.4ex}{$\leftarrowtriangle$}\cr}}
    {\ooalign{\raisebox{-.2ex}{$\rightarrowtriangle$}\cr\raisebox{.4ex}{$\leftarrowtriangle$}\cr}}
    {\ooalign{\raisebox{-.1ex}{$\scriptstyle\rightarrowtriangle$}\cr\raisebox{.35ex}{$\scriptstyle\leftarrowtriangle$}\cr}}
    {\ooalign{\raisebox{-.1ex}{$\scriptscriptstyle\rightarrowtriangle$}\cr\raisebox{.3ex}{$\scriptscriptstyle\leftarrowtriangle$}\cr}}
}}
\begin{document}
$A\leftrightarrowtriangle B_{A\leftrightarrowtriangle B_{A\leftrightarrowtriangle B}}$
\end{document}

This solution does not work inside of an \xymatrix, probably due to the usage of \cr. — dremodaris, Sep 11 '23 at 17:25

score 2 · Answer 2 · answered Aug 30 '23 at 16:42

This is a job for \ialign rather than \ooalign.

\documentclass{article}
\usepackage{stmaryrd}
\makeatletter
\newcommand{\leftrightarrowstriangle}{%
  \mathrel{%
    \mathpalette\arrowstriangle@{\leftarrowtriangle\rightarrowtriangle}%
  }%
}
\newcommand{\rightleftarrowstriangle}{%
  \mathrel{%
    \mathpalette\arrowstriangle@{\rightarrowtriangle\leftarrowtriangle}%
  }%
}
\newcommand{\arrowstriangle@}[2]{\arrowstriangle@@#1#2}
\newcommand{\arrowstriangle@@}[3]{%
  \vbox{%
    \offinterlineskip
    \sbox\z@{$\m@th#1\rightarrowtriangle$}%
    \ialign{%
      $\m@th#1##$\cr % template
      #2\cr
      \noalign{\kern-0.4\ht\z@}
      #3\cr
    }%
  }%
}
\makeatother
\begin{document}
$A\leftrightarrowstriangle B_{A\leftrightarrowstriangle B_{A\leftrightarrowstriangle B}}$
$A\rightleftarrowstriangle B_{A\rightleftarrowstriangle B_{A\rightleftarrowstriangle B}}$
\end{document}

I'm accepting Sandy G's answer for being comprehensible and editable without far-reaching LaTeX expertise. — dremodaris, Sep 01 '23 at 12:09
@dremodaris If you like to dig holes with a fork and roll spaghetti with a spade… — egreg, Sep 01 '23 at 12:40

score 0 · Accepted Answer · answered Sep 11 '23 at 17:28

The following, based on Sandy G's approach, works and is compatible with \xymatrix:

\documentclass{article}
\usepackage[only,rightarrowtriangle,leftarrowtriangle]{stmaryrd}
\newcommand{\stackedarrowstriangle}[2]{\mathrel{\mathchoice
    {\mathrlap{\raisebox{.35ex}{$#1$}}\raisebox{-.35ex}{$#2$}}
    {\mathrlap{\raisebox{.35ex}{$#1$}}\raisebox{-.35ex}{$#2$}}
    {\mathrlap{\raisebox{.25ex}{$\scriptstyle#1$}}\raisebox{-.25ex}{$\scriptstyle#2$}}
    {\mathrlap{\raisebox{.2ex}{$\scriptscriptstyle#1$}}\raisebox{-.2ex}{$\scriptscriptstyle#2$}}
}}
\newcommand{\rightleftarrowstriangle}{\stackedarrowstriangle{\rightarrowtriangle}{\leftarrowtriangle}}
\newcommand{\leftrightarrowstriangle}{\stackedarrowstriangle{\leftarrowtriangle}{\rightarrowtriangle}}
\begin{document}
$A\leftrightarrowtriangle B_{A\leftrightarrowtriangle B_{A\leftrightarrowtriangle B}}$
\end{document}

\rightleftarrows in the style of \rightarrowtriangle

3 Answers3