aits</span><span class="special">::</span><span class="identifier">create_generator_exists</span></code>
                returns <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></code>) or a <a class="link" href="basics.html#spirit.karma.reference.basics.lazy_argument">Lazy
                Argument</a> that evaluates to any type for which a mapping to
                a generator type is defined (the meta function <code class