typename UnaryReturn<PMatrix<T1,N,C>, OpUnaryMinus>::Type_t  d;
typename BinaryReturn<PMatrix<T1,N,C>, PMatrix<T2,N,C>, OpSubtract>::Type_t  d;
operator-(const PMatrix<T1,N,C>& l){  typename UnaryReturn<PMatrix<T1,N,C>, OpUnaryMinus>::Type_t  d;  for(int i=0; i < N; ++i)    for(int j=0; j < N; ++j)      d.elem(i,j) = -l.elem(i,j);  return d;}