\myheading{Switching value trick}

... found in Jorg Arndt --- Matters Computational / Ideas, Algorithms, Source Code
\footnote{\url{https://www.jjj.de/fxt/fxtbook.pdf}}.

You want a variable to be switching between 123 and 456.
You may write something like:

\begin{lstlisting}
if (a==123)
    a=456;
else
    a=123;
\end{lstlisting}

But this can be done using a single operation:

\lstinputlisting[style=customc]{bool/XOR/XOR_switch.c}

It works because $123 \oplus 123 \oplus 456=0 \oplus 456=456$ and
$456 \oplus 123 \oplus 456=456 \oplus 456 \oplus 123=0 \oplus 123=123$.

One can argue, worth it using or not, especially keeping in mind code readability.
But this is yet another demonstration of XOR properties.