
<div class="info-desc">
<p><code class="code">sub&nbsp;s&nbsp;~pos&nbsp;~len</code> is a string of length <code class="code">len</code>, containing the
    substring of <code class="code">s</code> that starts at position <code class="code">pos</code> and has length
    <code class="code">len</code>.</p>
</div>
<ul class="info-attributes">
<li><b>Raises</b> <code>Invalid_argument</code> if <code class="code">pos</code> and <code class="code">len</code> do not designate a valid
    substring of <code class="