de></dt><dt class="spec value" id="val-is_null"><a href="#val-is_null" class="anchor"></a><code><span class="keyword">val</span> is_null : <span><span class="type-var">'a</span> <a href="index.html#type-ptr">ptr</a></span> <span>&#45;&gt;</span> bool</code></dt><dt class="spec value" id="val-reference_type"><a href="#val-reference_type" class="anchor"></a><code><span class="keyword">val</span> reference_type : <span><span class="type-var">'a</span> <a href="index.html#type-ptr">ptr</a></span> <span>&#45;&gt