How to stack three relations

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?

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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 0:59
@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 1:04 mathtools provides \xleftrightarrow[under]{over}. May be that's what you are looking for. – Manuel Jan 13 '13 at 1:09 2 Answers \documentclass{article} \usepackage{mathtools,amssymb} \begin{document} $x \mathrel{\substack{R\\\rightleftarrows\\ L}} y$ $x \mathrel{\substack{R\\\longleftrightarrow\\L}} y$ \end{document}  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}  Hope this will get you started :-) - Thank you very much, this did it for me! – Olivier Bégassat Jan 13 '13 at 1:16 Do you know if I can get a long version of the \rightleftarrows somehow? – Olivier Bégassat Jan 13 '13 at 1:20 Are you writing the code yourself? I'm currently using the code for a blogpost edited with wordpress, will I be able to use it in this environment? I'll definitely use it further down the line on a proper Latex compiler, just so you know your efforts will not be wasted :) – Olivier Bégassat Jan 13 '13 at 1:27 That is fantastic :D thank you very much Harish Kumar! – Olivier Bégassat Jan 13 '13 at 1:35 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\,}\$

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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 1:17