Hi List, I created a (stl vector) of matrix_rows from the boost uBLAS. This seems to work fine. But somehow, the interplay with the stl algorithms seems then not to work. If I compile the code, i would expect a list of all the rows, ordered by the first row entry. But to sort algorithms seems to create multiple copies of the same matrix row. Can someone tell me, what is going wrong there? I'm using the gcc version 4.0.2 20050901 (prerelease) (SUSE Linux). Many thanks for advises how to make this work. Here the Code: #include <boost/numeric/ublas/matrix.hpp> #include <boost/numeric/ublas/matrix_proxy.hpp> #include <boost/numeric/ublas/io.hpp> #include <vector> #include <algorithm> namespace num = boost::numeric::ublas; typedef num::matrix<double> matrix_type; typedef num::matrix_row<matrix_type> matrix_row; typedef std::vector<matrix_row> data_proxy; template <int N> class Ordering { public: bool operator()(const matrix_row& row_1, const matrix_row& row_2) { return row_1(N) < row_2(N); } }; int main(int argc, char* argv) { const size_t N_1 = 25; const size_t M_1 = 10; const size_t N_2 = 20; const size_t M_2 = 10; matrix_type Data_1(N_1, M_1); matrix_type Data_2(N_2, M_2); data_proxy my_proxy; for (size_t i = 0; i < N_1; ++i) { Data_1(i, 0) = i; my_proxy.push_back(matrix_row(Data_1, i) ); } for (size_t j = 0; j < N_2; ++j) { Data_2(j, 0) = 0.5 + j; my_proxy.push_back(matrix_row(Data_2, j) ); } data_proxy copy(my_proxy); std::sort(my_proxy.begin(), my_proxy.end(), Ordering<0>() ); for (size_t i = 0; i < my_proxy.size(); ++i) { std::cout << my_proxy[i] << std::endl; } }