# How to create a backslash fraction?

How does one produce a backslash fraction? That is, something like 2\1 with the 1 above the 2.

• Please draw a picture. – MaestroGlanz Oct 19 '16 at 14:25
• Do you mean \frac{1}{2}, using amsmath ? – Andrew Oct 19 '16 at 14:33
• Interesting idea, but also (I'm just curious) why would you write a fraction this way? I spend so much time in classes trying to get the students not to use a slanted lines for fractions 'cause it inevitably leads to all sorts of mistakes. Or, does it have special meaning? – A.Ellett Oct 19 '16 at 22:06
• @A.Ellett I think it was the musical time-signature notation used by that famous American composer, Burt Back-a-frac. ;^) – Steven B. Segletes Oct 21 '16 at 14:43
• @A.Ellett It was my cheap-ass work-around for How to diagonally divide a table cell … properly? – Jim Mar 5 '18 at 21:24

I chose to use math mode to set the argument of \bsfrac, even though I notice that \nicefrac sets in text mode. The behavior can be changed for \bsfrac with the removal of the $ characters. \documentclass{article} \usepackage{graphicx,nicefrac} \newcommand\bsfrac{% \scalebox{-1}{\nicefrac{\scalebox{-1}{$#1$}}{\scalebox{-1}{$#2$}}}% } \begin{document} A nice fraction: \nicefrac{55}{23} or \nicefrac{$(x-1)$}{$x$}. And here is \bsfrac{55}{23} or \bsfrac{(x-1)}{x}. \end{document} One can simplify the definition as \newcommand\bsfrac{\reflectbox{\nicefrac{\reflectbox{$#1$}}{\reflectbox{$#2$}}}}  or even, as Máté suggests, \newcommand\bsfrac{\reflectbox{\nicefrac[\reflectbox]{$#1$}{$#2$}}}  • Oh, that's what the bs stands for... – MCMastery Oct 19 '16 at 18:39 • @MCMastery Apparently, my efforts to use mnemonic devices to name macros sometimes can be misunderstood...tex.stackexchange.com/questions/167670/… – Steven B. Segletes Oct 19 '16 at 18:42 • You can even further shorten the definition of bsfrac to \newcommand{\bsfrac}{\reflectbox{\nicefrac[\reflectbox]{#1}{#2}}} – Máté Wierdl Sep 20 '17 at 11:47 A shorter less elegant way is to simply use: $^1$/$_2$%or$_1 \backslash ^2\$