key,
there is no captured value.
</p>


<h3><a name="cap-func"></a><code>patt / function</code></h3>
<p>
Creates a <em>function capture</em>.
It calls the given function passing all captures made by
<code>patt</code> as arguments,
or the whole match if <code>patt</code> made no capture.
The values returned by the function
are the final values of the capture.
In particular,
if <code>function</code> returns no value,
there is no captured value.
</p>


<h3><a name="matchtime"></a><code>lpeg.Cmt(patt, function)