# Floating point square root symbol

For my numerical analysis class, we use a certain symbol to represent the floating point square root operation (similar to using \ominus for floating point subtraction, \oplus for floating point addition, etc.). In order to render this in a LaTeX document, I'd need to somehow draw a similarly-sized circle over the "v" part of the square root symbol, but I'm not too familiar with tikz and don't really know how to start working on this.

The most important aspect is making sure the circle has the same size as the one for the \oxxxx symbols. How would I go about making this? (And potentially, is there a better, more standard way to denote this operation?)

## Edit

Added a picture to make what I'm asking for a tiny bit clearer.

• First, look at the Comprehensive LaTeX Symbol List (ctan.org/pkg/comprehensive?lang=en). Could you scan and post an image as part of your question? Commented Nov 21, 2018 at 21:16
• The symbol is not in the Symbol List sadly, I already checked before posting, hence the softer part of my question asking about the more standard notation for this. Commented Nov 21, 2018 at 21:21
• do you need it to work like \sqrt growing in size and with an extending bar while still having the circle, or simpler case of just needing a fixed √ Commented Nov 21, 2018 at 21:23
• @DavidCarlisle Ideally, it would work like \sqrt, while having the circle grow in a way similar to how the circle gets bigger when going from \oplus to bigoplus. The last part, about the circle growing, is purely aesthetic (but would still be greatly appreciated), the bar growing is a requirement. Commented Nov 21, 2018 at 21:26
• If you really want a “custom” root sign that behaves exactly as the original, that is, that grows automatically with the size of the subformula it covers, I think that, all things considered, the simplest solution is to use a virtual font. I haven’t got time to write an answer now, but I can suggest this example of a similar problem which I solved by means of this technique; that answer contain further links that you might find useful.
– GuM
Commented Nov 21, 2018 at 22:25

This is really just for fun (and because this is tagged TikZ). An attempt to adapt the shape of the circle to the dimensions of the square root. The idea is to use a path picture to find out what the dimensions of the square root are. Luckily tikzmark has the cool feature of detecting the mode we are in, so we do not have to worry about this here.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{tikzmark,calc}
\newcounter{stuff}
\tikzset{oroot/.style={path picture={\draw
let \p1=($(path picture bounding box.north)-(path picture bounding box.south)$) in (path picture bounding box.west)
arc(180:-180:{0.25em+\y1/10} and \y1/3);}}}
\begin{document}
abc  $\tikzmarknode[oroot]{1}{\sqrt{a+b}}$
$\tikzmarknode[oroot]{2}{\sqrt{\frac{\frac{1}{12}}{\frac{a}{b}}}}$
\end{document}


I can offer this one, but don't try it with big arguments to the square root such as fractions.

\documentclass{article}
\usepackage{amsmath}
\usepackage{graphicx}

\newcommand{\fpsqrt}[1]{%
\sqrt[\leftroot{-5}\uproot{-7}\scalebox{0.7}{$\bigcirc$}]{\mathstrut#1}%
}

\begin{document}

$\fpsqrt{120}$

\end{document}