 Parsers and generators in <a href="http://boost-spirit.com" target="_top">Spirit</a>
          are fully attributed. <span class="emphasis"><em>Spirit.Qi</em></span> parsers always <span class="emphasis"><em>expose</em></span>
          an attribute specific to their type. This is called <span class="emphasis"><em>synthesized
          attribute</em></span> as it is returned from a successful match representing
          the matched input sequence. For instance, numeric parsers, such as <code class="comput