allayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Y<span class="special">&gt;</span> <a name="idp56980272-bb"></a><span class="identifier">weak_ptr</span><span class="special">(</span><a class="link" href="weak_ptr.html" title="Class template weak_ptr">weak_ptr</a><span class="special">&lt;</span> <span class="identifier">Y</span><span class="special">,</span> <span class="identifier">A</span><span class="special">,</span> <span class="iden