ector.</td>
</tr>

<tr>
<td><code>size_type size () const</code></td>
<td>Returns the size of the sub vector.</td>
</tr>

<tr>
<td><code>const_reference operator () (size_type i)
const</code></td>
<td>Returns the value of the <code>i</code>-th element.</td>
</tr>

<tr>
<td><code>reference operator () (size_type i)</code></td>
<td>Returns a reference of the <code>i</code>-th element.</td>
</tr>

<tr>
<td><code>matrix_column &amp;operator = (const matrix_column
&amp;mc)</code></td>
<td>The assignment operator