Does anyone have an idea why the following doesn&#39;t compile:<br />	using lambda::_1;<br />	using lambda::_2;<br />	boost::function&lt;double (const boost::array&lt;double, 2&gt;&)&gt; f = lambda::ret&lt;double&gt;(_1[0] * _1[1]);<br /><br />But the following does as a double-check:<br />	using lambda::_1;<br />	using lambda::_2;<br />	boost::function&lt;double (const double&, const double&)&gt; f2 = lambda::ret&lt;double&gt;(_1 * _2);<br /><br />Thanks,<br />Jesse