Concept definition

template<typename MA, typename MB, typename MC>
concept detray::concepts::matrix_multipliable_into = 
    matrix_multipliable<MA, MB> && matrix_compatible<MA, MC> &&
    matrix_compatible<MB, MC> && (traits::rows<MC> == traits::rows<MA>) &&
    (traits::columns<MC> == traits::columns<MB>) &&
    requires(traits::scalar_t<MA> sa, traits::scalar_t<MB> sb,
             traits::scalar_t<MC>& sc) {
      { sc += (sa * sb) };
    }