QVM: Quaternions, Vectors, Matrices

namespace boost
{
    namespace qvm
    {
        //Only enabled if: is_quat<A>::value
        template <class A>
        -unspecified-return-type- qref( A & a );
    }
}

Returns:

An identity view proxy of a; that is, it simply accesses the elements of a.

This allows calling Boost QVM operations when a is of built-in type, for example a plain old C array.