       returns 0.
        </p>
<h6>
<a name="json.ref.boost__json__object.empty.h2"></a>
          <span class="phrase"><a name="json.ref.boost__json__object.empty.complexity"></a></span><a class="link" href="empty.html#json.ref.boost__json__object.empty.complexity">Complexity</a>
        </h6>
<p>
          Constant.
        </p>
<h6>
<a name="json.ref.boost__json__object.empty.h3"></a>
          <span class="phrase"><a name="json.ref.boost__json__object.empty.exception_safety"></a></span><a class="link" h