[Boost-users] [exception] array tags

Hi, I have just discovered boost::exception and am very happy I did. One thing i would like to do, but haven't yet figure out: I have a matrix class for which I want to throw exceptions when out_of_range requests are made. One of the extra tags I want to attach is the dimensions of the matrix and it would be neat if i can put those in an array. Defining the tag is no problem, getting the info in there is: defining: typedef boost::error_info std_range_size; I have tried: << std_range_size({m_nRows, m_nCols}); size_t a[2] = {m_nRows, m_nCols}; << std_range_size(a); and desperately even << std_range_size() = {m_nRows, m_nCols}; which doesn't make much sense Can I do such a thing, should I use something else than a plain array or do i have to resort to two separate tags for nRows adn nCols respectively? Thank you for your help and advice! Best, Diederick