> is an expression of type <code>array[i] T</code> with <code>i</code> and <code>k</code>
expressions of type <code>int</code>, then <code>e[k]</code> is of type <code>T</code>,</li>
<li>if <code>e</code> has implementation type <code>vector</code> or <code>row_vector</code>,
dimensionality 0, then <code>e[i]</code> has implementation type <code>real</code>,</li>
<li>if <code>e</code> has implementation type <code>matrix</code>, then <code>e[i]</code> has type
<code>row_vector</code>,</li>
<li>if <code>e</c