Lets say I have a simple calculator grammar like the one defined in trunk\libs\spirit\example\fundamental\calc_plain.cpp<br><br>Now I would like to extend that grammar e.g. add support for sqrt() <br><br>One way would be modifying the existing grammar class (patch provided)<br> <br>But what I would like is to create a new class that uses or inherits from the existing grammar class to provide the extended behavior. <br><br>That is, I would need both the calculator and the extended_calculator classes available, and without code duplication.<br> <br>�Is this possible?<br><br>