><span class="special">;</span> <span class="comment">// OK, widening conversion.</span>
<span class="identifier">d</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">*</span> <span class="identifier">b</span><span class="special">;</span>  <span class="comment">// OK, can convert from an expression template too.</span>
</pre>
<p>
      However conversions that are inherently lossy are either declared explicit
      or else forbidden altogether:
    </p>
<pre class