class="code">fill&nbsp;s&nbsp;start&nbsp;len&nbsp;c</code> modifies <code class="code">s</code> in place, replacing <code class="code">len</code>
    characters with <code class="code">c</code>, starting at <code class="code">start</code>.</p>

<p>Raise <code class="code"><span class="constructor">Invalid_argument</span></code> if <code class="code">start</code> and <code class="code">len</code> do not designate a
    valid range of <code class="code">s</code>.</p>
</div>
</div>

<pre><span id="VALblit"><sp