When I google this, it seems that \XOR is how you would get an XOR symbol in LaTeX, however that is giving me the 'undefined control sequence' error. How does one get the xor symbol?
[Tex/LaTex] Logic operators in LaTeX? (XOR?)
symbols
Related Solutions
You want to use \bigoplus instead of \oplus.
I've never seen concatenation done that way. Addition and XOR are commutative operations so it makes sense to sum over a set (or take the exclusive OR of a set). Concatenation is not like that. I think I would explicitly write out the concatenation. That said, you can use \bigparallel from the stmaryrd package.
\documentclass{article}
\usepackage{amsmath}
\usepackage{stmaryrd}
\newcommand*\concat{\mathbin{\|}}
\begin{document}
\[x_1\concat x_2\concat\dotsb\concat x_n\]
\[\bigparallel_{i=1}^n x_i\]
\end{document}
The best idea I think is to define the XOR in such a way that automatically the + sign is inside the circle. One possibility is:
\tikzset{XOR/.style={draw,circle,append after command={
[shorten >=\pgflinewidth, shorten <=\pgflinewidth,]
(\tikzlastnode.north) edge (\tikzlastnode.south)
(\tikzlastnode.east) edge (\tikzlastnode.west)
}
}
}
The complete example:
\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{shapes,arrows,fit,calc,positioning,automata}
\begin{document}
\tikzset{XOR/.style={draw,circle,append after command={
[shorten >=\pgflinewidth, shorten <=\pgflinewidth,]
(\tikzlastnode.north) edge (\tikzlastnode.south)
(\tikzlastnode.east) edge (\tikzlastnode.west)
}
}
}
\tikzset{line/.style={draw, -latex',shorten <=1bp,shorten >=1bp}}
\begin{tikzpicture}[auto]
\node (XOR-aa)[XOR,scale=1.2] {};
\node [above of=XOR-aa,node distance=1.5cm,text width=1.5cm,anchor=south,align=center] (bla) {Bla};
\node [right of=XOR-aa,node distance=3cm,text width=1.5cm,anchor=east,align=center] (Blob) {Blob};
\node [left of=XOR-aa,node distance=3cm,text width=1.5cm,anchor=west,align=center] (blubb) {Blubb};
\path[line] (XOR-aa) edge (Blob)
(bla) edge (XOR-aa)
(blubb) edge (XOR-aa);
\end{tikzpicture}
\end{document}
Notice in particular how the line is defined:
\tikzset{line/.style={draw, -latex',shorten <=1bp,shorten >=1bp}}
The shorten allows that the arrows does not touch the XOR: without this, a departing arrow could be confused with the the +.
The result is:
The approach allows to scale the XOR symbol very easily without problems; for example using:
\node (XOR-aa)[XOR,scale=2.5] {};
in the previous MWE leads to:
Best Answer
How about
\newcommand*\xor{\oplus}?