{ //snip constructors
Hi Everybody, I'm trying to implement a proxy_iterator for ublas::matrix which should behave as an iterator over the matrix rows. My "obvious" solution does not seem to work: typedef boost::numeric::ublas::matrix<double> Matrix; typedef boost::numeric::ublas::matrix_row<Matrix> MatrixRow; typedef boost::numeric::ublas::vector<double> Vector; struct MatrixIterator: public boost::iterator_facade< MatrixIterator, Vector,//the semantic value type is a Vector boost::random_access_traversal_tag, MatrixRow//reference is a row of a matrix private: friend class boost::iterator_core_access; //snip iterating stuff //fun part MatrixRow dereference() const { return row(*m_matrix,m_element); } std::size_t m_element; Matrix* m_matrix; }; which reuslts in an error that MatrixRow can't be implicitely casted to Vector. Which is correct. At the moment I'm using a 90% hacked workaround which changes the ValueType of the Iterator to MatrixRow. This seems to work as long as I don't use algorithms which rely on the actual value_type of the iterator (for example iter_swap as implemented in the gnu libstdc++ will fail miserably even though a correct swap is implemented for the MatrixRow...different story ) Since I need std::random_shuffle I am out of luck. I tried to find the actual requirements of iterator_facade with respect to ValueType/ReferenceType in the documentation, but was not able to find them. Does someone now a solution to this problem which works and results in an iterator which can safely be used in random_shuffle? Or can point me to the correct requirements? Greetings from Germany, Oswin Krause