QVM: Quaternions, Vectors, Matrices

col

#include <boost/qvm/map_mat_vec.hpp>

namespace boost
{
    namespace qvm
    {
        //Only enabled if: is_mat<A>::value
        template <int C,class A>
        -unspecified-return-type- col( A & a );
    }
}

The expression col<C>(m) returns a view proxy that accesses column C of the matrix m as a vector.