>n</sub></em>,
this capture will produce the value
<em>func(...func(func(C<sub>1</sub>, C<sub>2</sub>), C<sub>3</sub>)...,
         C<sub>n</sub>)</em>,
that is, it will <em>fold</em>
(or <em>accumulate</em>, or <em>reduce</em>)
the captures from <code>patt</code> using function <code>func</code>.
</p>

<p>
This capture assumes that <code>patt</code> should produce
at least one capture with at least one value (of any type),
which becomes the initial value of an <em>accumulator</em>.
(If you need a specific 