as indexes must denote either an integer
(<code>int</code>) or an integer array (<code>int[]</code>). Expressions
participating in range indexes (e.g., <code>a</code> and <code>b</code> in
<code>a : b</code>) must denote integers (<code>int</code>).</p>
<p>A second condition is that there not be more indexes provided than
dimensions of the underlying expression (in general) or variable (on
the left side of assignments) being indexed. A vector or row vector
adds 1 to the array dimension and a matrix adds 2. 