 = x = \eps + x\)</span>.
So we have a <a class="reference external" href="https://en.wikipedia.org/wiki/Monoid"><em>monoid</em></a></p>
<div class="math notranslate nohighlight">
\[
(\words, +, \eps)
\]</div>
</div>
</div><p>This means that we can “add” programs (since they are words).  For example, let</p>
<div class="math notranslate nohighlight">
\[
q =copyprog_{1,2,3} + \moveprog_{2,1}
\]</div>
<p>This program <span class="math notranslate nohighlight">\(q\)</span> would take the contents of regist