on_library.tti_nested_type.checking_if_the_member_type_exists">Checking
      if the member type exists</a>
    </h4>
<p>
      Once we use BOOST_TTI_MEMBER_TYPE to generate a nested type if it exists we
      will normally use that type in further metafunction programming. Occasionally,
      given the type we generate, we will want to ask if the type is really our nested
      type or the marker type instead. Essentially we are asking if the type generated
      is the marker type or not. If it is the mar