plicitly
        become slots, because slots are no longer comparable.  </p>
<p> The second obvious addition when one has
        <code class="computeroutput">operator+=</code> would be to add a <code class="computeroutput">+</code>
        operator that supports addition of multiple slots, followed by
        assignment to a signal. However, this would require
        implementing <code class="computeroutput">+</code> such that it can accept any two
        function objects, which is technically infeasible