ht-hand side is evaluated first, it is possible to
increment a variable in Stan just as in C++ and other programming
languages by writing</p>
<pre class="stan"><code>n = n + 1;</code></pre>
<p>Such self assignments are not allowed in BUGS, because they induce a
cycle into the directed graphical model.</p>
<p>The left-hand side of an assignment may contain indices for array,
matrix, or vector data structures. For instance, if <code>Sigma</code> is
of type <code>matrix</code>, then</p>
<pre class="stan"><code