="special">.</span><span class="identifier">set_age</span><span class="special">(</span><span class="identifier">val</span><span class="special">),</span> <span class="identifier">keys</span><span class="special">::</span><span class="identifier">age</span><span class="special">))</span>

<span class="identifier">demo</span><span class="special">::</span><span class="identifier">employee</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="ide