 If
a non-<code>NULL</code> value is supplied, it will be used, even if it makes no sense
in relation to value of <code>unit</code>.</p></dd>

</dl></div>
    <div class="section level2">
    <h2 id="value">Value<a class="anchor" aria-label="anchor" href="#value"></a></h2>
    <p>A <code><a href="https://rdrr.io/r/base/list.html" class="external-link">list()</a></code> of two items: <code>unit</code> which is an
<code><a href="https://rdrr.io/r/base/expression.html" class="external-link">expression()</a></c