How do I put a circle around an operator?

Question

For example, I want to put a circle around \land, just like one can put a circle around + by writing \oplus. Is there a general method to do this?

Answer 1

Here's a version combining \land and \bigcirc:

\makeatletter
\newcommand\incircbin
{%
  \mathpalette\@incircbin
}
\newcommand\@incircbin[2]
{%
  \mathbin%
  {%
    \ooalign{\hidewidth$#1#2$\hidewidth\crcr$#1\bigcirc$}%
  }%
}
\newcommand{\oland}{\incircbin{\land}}
\makeatother

It will change size according to math style:

\[a\oland b\frac{a\oland b}{a\oland b^{a\oland b^{a\oland b}}}\] 

gives

Answer 2

Update

More correct is the next code, I used the code from egreg here

\documentclass{article}
\usepackage{amssymb,amsmath}
\usepackage{tikz}

\newcommand{\circleland}{ 
  \mathbin{
    \mathchoice
      {\buildcircleland{\displaystyle}}
      {\buildcircleland{\textstyle}}
      {\buildcircleland{\scriptstyle}}
      {\buildcircleland{\scriptscriptstyle}}
  } 
}

\newcommand\buildcircleland[1]{%
  \begin{tikzpicture}[baseline=(X.base), inner sep=0, outer sep=0]
    \node[draw,circle] (X)  {$#1\land$};
  \end{tikzpicture}%
}

\begin{document}

\[a\circleland b\frac{a\circleland b}{a\circleland b^{a\circleland b^{a\circleland b}}}\]    

$x \circleland (y\circleland z)$ and  $x \land (y\land z)$     
\end{document} 

Answer 3

You can use pgf for this purpose by defining a new command:

\newcommand{\circleland}{
\tikz{
\pgfsetbaselinepointlater{\pgfpointanchor{X}{base}}
\pgfcircle{\pgfpointorigin}{0.15cm}
\pgfusepath{stroke}
\node (X) {$\land$};
}}

Look at this MWE:

\documentclass{article}
\usepackage{amssymb,amsmath}
\usepackage{tikz}

\newcommand{\circleland}{
\tikz{
\pgfsetbaselinepointlater{\pgfpointanchor{X}{base}}
\pgfcircle{\pgfpointorigin}{0.15cm}
\pgfusepath{stroke}
\node (X) {$\land$};
}}
\begin{document}
\[x \land y\]

\begin{equation}
x \circleland y
\end{equation}

\end{document} 

the result will be:

Answer 4

I am giving the general answer to the question (valid for any operator and even text) by slightly modifying Alain's code.

\documentclass{article}

\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{wasysym}
\usepackage{tikz}

%The given symbol or text (\text{mytext}) in a circle
%To be used always in math mode
\newcommand{\circlesign}[1]{ 
    \mathbin{
        \mathchoice
        {\buildcirclesign{\displaystyle}{#1}}
        {\buildcirclesign{\textstyle}{#1}}
        {\buildcirclesign{\scriptstyle}{#1}}
        {\buildcirclesign{\scriptscriptstyle}{#1}}
    } 
}

\newcommand\buildcirclesign[2]{%
    \begin{tikzpicture}[baseline=(X.base), inner sep=0, outer sep=0]
    \node[draw,circle] (X)  {\ensuremath{#1 #2}};
    \end{tikzpicture}%
}


\begin{document}

    $\circlesign{+} \neq \oplus$,  $\circlesign{\bullet} \neq \odot$ \\
    Put whatever you want inside the circle $\circlesign{\davidsstar}$

    $\circlesign{\text{whatever!}}$

\end{document}

Answer 5

I spent some time trying to get the <,<=,=,>= and > operators circled nicely. Code ended up a bit hacky, even though it worked:

<

\Large \textcircled{\normalsize \$\hspace{0.05 mm} <\$} \normalsize

<=

\Large \textcircled{\raisebox{1pt} {\normalsize \$\hspace{0.05 mm} \leq\$}} \normalsize

=

\Large \textcircled{\raisebox{1pt} {\normalsize \$\hspace{0.05 mm} =\$}} \normalsize

>=

\Large \textcircled{\raisebox{1pt} {\normalsize \$\hspace{0.1 mm} \geq\$}} \normalsize

>

\Large \textcircled{\normalsize \$\hspace{0.1 mm} >\$} \normalsize

The horizontal spacings are quite finicky. It ended up looking like this (center column):

Answer 6

Thanks for the great answers! However, Stephan's original code produced an error in my project ("Illegal parameter number in definition of \reserved@a"). I did not figure out what exactly the problem was. I solved it by adding some \protects, which seems to be a bit more robust. Here is my version of the MWE:

\documentclass{article}
\usepackage{amssymb,amsmath}

\newcommand{\incircbin}[1]{%
  \mathbin{%
    \mathchoice%
    {\protect\incircint{\displaystyle}{#1}}%
    {\protect\incircint{\textstyle}{#1}}%
    {\protect\incircint{\scriptstyle}{#1}}%
    {\protect\incircint{\scriptscriptstyle}{#1}}%
  }%
}
\newcommand{\incircint}[2]{%
  \ooalign{$#1\bigcirc$\crcr\hidewidth$#1#2$\hidewidth\crcr}%
}
\newcommand{\circleland}{\incircbin{\land}}

\begin{document}

\[a\circleland b\frac{a\circleland b}{a\circleland b^{a\circleland b^{a\circleland b}}}\]    

\end{document} 

Matthias

Answer 7

For me the idea from here was very useful:

\documentclass{article}
\usepackage{tikz}
\newcommand*\circled[1]{\tikz[baseline=(char.base)]{\node[draw,circle,thick,blue,text=black] (char) {#1};}}
\begin{document}
\noindent
Text: \circled{=} \newline
Math: $\circled{\textbf{=}}$
\end{document}

Answer 8

The other approaches weren't working for me because I was working in an environment where I couldn't define new macros or import packages. So my solution was to simply overlay \bigcirc and the symbol that I want inside the circle, in this case a <, by using \hspace to shift the inner symbol until it is aligned.

$\bigcirc\hspace{-12pt}<$

The result looks reasonable:

This approach takes a lot of manually fiddling, however, to make different symbols properly centered.