ass="keyword">typename</span> IndexExpression<span class="special">&gt;</span> 
  <span class="emphasis"><em><span class="identifier">unspecified</span></em></span> <a name="idp53592336-bb"></a><span class="keyword">operator</span><span class="special">[</span><span class="special">]</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">IndexExpression</span> <span class="special">&amp;</span> expr<span class="special">)</span> <span class="keyword">const</span><spa