eclared to have type
<code>row_vector</code> and <code>Y</code> is a variable declared as type
<code>matrix</code>, then the following sequence of statements to swap the
first two rows of <code>Y</code> is well formed.</p>
<pre class="stan"><code>x = Y[1];
Y[1] = Y[2];
Y[2] = x;</code></pre>
<div id="lvalue-summary" class="section level3">
<h3 class="unnumbered" number="">Lvalue Summary</h3>
<p>The expressions that are legal left-hand sides of assignment
statements are known as “lvalues.” In Stan, there