s="special">::</span><span class="identifier">value_ref</span><span class="special">&lt;</span> <span class="identifier">point</span> <span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">value</span><span class="special">)</span> <span class="keyword">const</span>
    <span class="special">{</span>
        <span class="keyword">if</span> <span class="special">(</span><span class="identifier">value</span><span class="special">)</span>