>Iterator</span> <span class="identifier">last</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;&amp;</span> <span class="identifier">v</span><span class="special">)</span>
<span class="special">{</span>
    <span class="keyword">using</span> <span class="identifier">x3</span><span class="special">::</span><span class="ident