<span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">if_</span><span class="special"><</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">is_sequence</span><span class="special"><</span> <span class="identifier">extracted_type</span> <span class="special">></span><span class="special">,</span> <span class="identifier">value_ref</span><span class="special"><</span> <span class="identifier">extracted_type</span><span class="special">,</span> <span class="identifier">TagT</span> <span class="special">></span><span class="special">,</span> <span class="identifier">extracted_type</span> <span class="keyword">const</span> <span class="special">&</span> <span class="special">></span><span class="special">::</span><span class="identifier">type</span> <a name="boost.log.result_of.extract_or_default.type"></a><span class="identifier">type</span><span class="special">;</span>
<span class="special">}</span><span class="special">;</span></pre></div>
<div class="refsect1">
-<a name="idp98576992"></a><h2>Description</h2>
+<a name="idp109198384"></a><h2>Description</h2>
<p>The metafunction results in a type that is in form of <code class="computeroutput">T const&</code>, if <code class="computeroutput">T</code> is not an MPL type sequence and <code class="computeroutput">DefaultT</code> is the same as <code class="computeroutput">T</code>, or <code class="computeroutput">value_ref< TypesT, TagT ></code> otherwise, with <code class="computeroutput">TypesT</code> being a type sequence comprising the types from sequence <code class="computeroutput">T</code> and <code class="computeroutput">DefaultT</code>, if it is not present in <code class="computeroutput">T</code> already. </p>
</div>
</div>