ss="comment">//       well (see the typedef for the token_type below).</span>
<span class="comment">//</span>
<span class="comment">// The conversion of the matched input to an instance of this type occurs</span>
<span class="comment">// once (on first access), which makes token attributes as efficient as </span>
<span class="comment">// possible. Moreover, token instances are constructed once by the lexer</span>
<span class="comment">// library. From this point on tokens are passed by reference only, </spa