n the return type cannot be deduced. For example, suppose you have defined:

	</p>
<pre class="programlisting">C operator+(A, B);</pre>
<p>

	The following lambda function invocation fails, since the return type cannot be deduced:

	</p>
<pre class="programlisting">A a; B b; (_1 + _2)(a, b);</pre>
<p>
      </p>
<p>
	There are two alternative solutions to this. 
	The first is to extend the BLL type deduction system to cover your own types (see <a class="xref" href="extending.html" title="Extending return ty