s="code">i</code>.</p>
</div>
<ul class="info-attributes">
<li><b>Raises</b><ul><li><code>Not_found</code> if <code class="code">c</code> does not occur in <code class="code">s</code> after position <code class="code">i</code>.</li>
<li><code>Invalid_argument</code> if <code class="code">i</code> is not a valid position in <code class="code">s</code>.</li>
</ul></li>
</ul>
</div>

<pre><span id="VALindex_from_opt"><span class="keyword">val</span> index_from_opt</span> : <code class="type">string -&gt; int -