 passed value.
    </p>
<p>
      Note that if either member is a POD type, then that member is not zero-initialized
      by the <code class="computeroutput"><span class="identifier">compressed_pair</span></code> default
      constructor: it's up to you to supply an initial value for these types if you
      want them to have a default value.
    </p>
<p>
      Note that <code class="computeroutput"><span class="identifier">compressed_pair</span></code> can
      not be instantiated if either of the templ