#include <boost/type_traits/is_base_of.hpp>
#include <boost/utility/enable_if.hpp>

    // (t * m) [i] [j] = t * m [i] [j]
    template<class T1, class E2>
    BOOST_UBLAS_INLINE
    typename boost::disable_if<boost::is_base_of<matrix_expression<T1>,T1>,
	     typename matrix_binary_scalar1_traits<const T1, E2, scalar_multiplies<T1, typename E2::value_type> >::result_type
	       >::type
    operator * (const T1 &e1,
                const matrix_expression<E2> &e2) 
    {
        typedef typename matrix_binary_scalar1_traits<const T1, E2, scalar_multiplies<T1, typename E2::value_type> >::expression_type expression_type;
        return expression_type (e1, e2 ());
    }

    // (m * t) [i] [j] = m [i] [j] * t
    template<class E1, class T2>
    BOOST_UBLAS_INLINE
    typename boost::disable_if<boost::is_base_of<matrix_expression<T2>,T2>,
	     typename matrix_binary_scalar2_traits<E1, const T2, scalar_multiplies<typename E1::value_type, T2> >::result_type
	       >::type
    operator * (const matrix_expression<E1> &e1,
                const T2 &e2) {
        typedef typename matrix_binary_scalar2_traits<E1, const T2, scalar_multiplies<typename E1::value_type, T2> >::expression_type expression_type;
        return expression_type (e1 (), e2);
    }

    template<class E1, class E2>
    BOOST_UBLAS_INLINE
    typename matrix_matrix_binary_traits<typename E1::value_type, E1,
                                         typename E2::value_type, E2>::result_type
    operator* (const matrix_expression<E1> &e1,
          const matrix_expression<E2> &e2) {

      return prod(e1,e2);
    }