[GiNaC-list] extending the symbol

Hi, I am adding a light weight support for vector algebra in ginac. I am aware that it can be done through Clifford algebra, but the output is almost incomprehensible to debug. My problem is this. When a request like inner_product(lhs, rhs) is made, where one of lhs and rhs is not a vector, I would like to replace the inner_product with a regular product. How can I achieve this? I am planning to do it as follows 1) extend a symbol to a vector 2) determine if both lhs and rhs have a hanging vector by traversing the expressions in lhs and rhs and by testing for is_a<vector> Is there a better way to test if a symbol is a vector? If not what is the simplest way to extend symbol? thanks, Krishna.