    </p>
<p>
      One solution to this is afforded by the library itself. Given an enclosing
      type 'T' which we know must exist, either because it is a top-level type we
      know about or it is passed to us in some template as a 'class T' or 'typename
      T', and given an inner type named 'InnerType' whose existence we would like
      ascertain, we can use a <code class="computeroutput"><span class="identifier">BOOST_TTI_HAS_TYPE</span><span class="special">(</span><span class="identifier">InnerT