lue is passed into
          the semantic action. In <span class="emphasis"><em>Spirit.Karma</em></span> the opposite
          happens. Semantic actions are called before its associated generator is
          invoked. They may provide the data required by the generator.
        </p>
<p>
          The function/function object signature depends on the type of the generator
          to which it is attached. The generator <code class="computeroutput"><span class="identifier">double_</span></code>
          ex