Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

QVM: Quaternions, Vectors, Matrices

namespace boost
{
    namespace qvm
    {
        template <int R1,int R2>
        -unspecified-return-type- swap_rows();
    }
}

The expression swap_rows<R1,R2>(m) returns a view proxy that looks like the matrix m with rows R1 and R2 swapped.