Hello, let's say you have the following function void combine(boost::numeric::ublas::matrix<int> &m) { row(m, 1) += row(m, 2); } works great and adds the second row to the first one. But trying to xor the individual integers by using void combine(boost::numeric::ublas::matrix<int> &m) { row(m, 1) += row(m, 2); } fails, because the ^ operator isn't defined. In boost/numeric/ublas/matrix_proxy.hpp I've found the definitions of the plus, minus etc operators but at the moment I don't know what I have to define there. Can anybody help? Thanks a lot Florian