Hi, I am trying to use boost.compute to extend my linear algebra library to GPUs. so far it helped me a lot with vectors as i can directly use the iterator interface. Matrices are harder. for matrices i need to overload the operator matrix(i,j)-> return the element (i,j). For this i have to return an expression which then offers operator<< with meta_kernel, for example template inline meta_kernel& operator<<(boost::compute::detail::meta_kernel &kernel, const matrix_element_expr &expr) { return kernel << kernel.get_buffer_identifier<T>(expr.m_buffer, expr.m_address_space) << '[' << expr.m_expr1 <<"*" <