n><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">&amp;</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>

  <span class="comment">// <a class="link" href="variables_map.html#id-1_3_31_9_11_1_1_4_8-bb">friend functions</a></span>
  <span class="keyword">friend</span> <span class="identifier">BOOST_PROGRAM_OPTIONS_DECL</span> <span class="keywor