n>
<span class="comment">// avoiding them being copied around.</span>
<span class="identifier">lex</span><span class="special">::</span><span class="identifier">token_def</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;</span> <span class="identifier">identifier</span><span class="special">;</span>
<span class="identifier">lex</span><span class="special">::</span><span class="identifier">