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: