9

Is it possible to stack three relations or symbols ontop of one another? Specifically I would like to stack three symbols, R, \rightleftarrows and L in order to define a pair of adjoint functors $R:C\to D$ and $C\gets D:L$.

Also, is there a \rightleftarrow with long arrows? EDIT I actually meant to ask wether there is a version of \rightleftarrows with long arrows.

I'm not a regular user, so I don't know how to format my question adequately, could someone convert what's inside the dollar so that it appears as latex please?

Olivier Bégassat
  • 2,251
  • 2
    For the second question, you have \longleftrightarrow. Can you please elaborate on how should the symbols be stacked? Do you have an image of the desired result? – Gonzalo Medina Jan 13 '13 at 00:59
  • @GonzaloMedina Thanks for the command. I would like to have the R$ sit ontop of the leftrightarrow and the L to be below the longrightarrow. Similarly to when one writes \stackrel{def}{=} where the def sits atop the equality, I want the R to be where the def is in my example, and the L should be at the same place but below the equality sign. – Olivier Bégassat Jan 13 '13 at 01:04
  • mathtools provides \xleftrightarrow[under]{over}. May be that's what you are looking for. – Manuel Jan 13 '13 at 01:09

2 Answers2

15
\documentclass{article}
\usepackage{mathtools,amssymb}

\begin{document}
\[
x \mathrel{\substack{R\\\rightleftarrows\\ L}} y
\]

\[
x \mathrel{\substack{R\\\longleftrightarrow\\L}} y
\]
\end{document}

enter image description here

Edit:

Some hack wrote in a hurry to make long version of \rightleftarrows:

\documentclass{article}
\usepackage{mathtools,amssymb}
\newcommand{\myrightleftarrows}{\mathrel{\substack{\longrightarrow \\[-.6ex] \longleftarrow}}}

\begin{document}

\[
x \mathrel{\substack{R\\\myrightleftarrows\\L}}  y
\]
%
\[
x \mathrel{\substack{R\\\rightleftarrows\\ L}} y
\]
\end{document}

enter image description here

Hope this will get you started :-)

6

The mathtools package offers you \xleftrightarrow[<above>]{<below>}; for the second question, standard LaTeX has \longleftrightarrow:

\documentclass{article}
\usepackage{mathtools}

\begin{document}

$\longleftrightarrow\qquad\xleftrightarrow[L\,]{R\,}$

\end{document}

enter image description here

Gonzalo Medina
  • 505,128
  • Thank you very much for your answer, I tried using your formula but it didn't work for some reason, maybe it's because I'm using wordpress to write latex. – Olivier Bégassat Jan 13 '13 at 01:17