ctor must induce a strict weak ordering. Default: <code class="computeroutput"><span class="identifier">compare</span><span class="special">&lt;</span>
            <span class="identifier">std</span><span class="special">::</span><span class="identifier">less</span><span class="special">&lt;</span><span class="identifier">key_type</span><span class="special">&gt;</span>
            <span class="special">&gt;</span></code>
          </li>
<li class="listitem">
            <span class="bold"><strong><code cla