#include <boost/qvm/quat_operations.hpp>
namespace boost
{
    namespace qvm
    {
        //Only enabled if:
        //  is_quat<A>::value && is_quat<B>::value
        template <class A,class B>
        A & operator-=( A & a, B const & b );
    }
}
Subtracts the elements of b from the corresponding elements of a.
a.