    If you are using Visual C++ and have an error like:
    </p>
<pre class="programlisting">error C2664: 'bool boost::function4&lt;R,T0,T1,T2,T3&gt;::operator ()(T0,T1,T2,T3) const' :
    cannot convert parameter 4 from '...' to '...'
</pre>
<p>
      or you are using GCC and have an error like:
    </p>
<pre class="programlisting">error: no match for call to '(const boost::function&lt;bool ()(...)&gt;) (...)'
note: candidates are: ... boost::function4&lt;R,T1,T2,T3,T4&gt;::operator()(T0,T1,T2,T3) const [w