s="p">;</span>         <span class="c1">// result of dereferencing</span>
  <span class="k">typename</span> <span class="n">difference_type</span><span class="p">;</span> <span class="n">where</span> <span class="n">PointNDConcept</span><span class="o">&lt;</span><span class="n">difference_type</span><span class="o">&gt;</span><span class="p">;</span> <span class="c1">// return value of operator-.</span>
  <span class="k">typename</span> <span class="n">const_t</span><span class="p">;</span>           <span