s, three from the array and two
from the matrix.</p>
<p>Recall that the array dimensions come before the matrix or vector
dimensions in an expression such as the following declaration of a
three-dimensional array of matrices.</p>
<pre class="stan"><code>matrix[M, N] a[I, J, K];</code></pre>
<p>The matrix <code>a</code> is indexed as <code>a[i, j, k, m, n]</code> with the array
indices first, followed by the matrix indices, with <code>a[i, j, k]</code>
being a matrix and <code>a[i, j, k, m]</code> being a ro