1. Rebind:
   • Map and rebind should not allocate memory

     typedef typename Blackbox::template rebind<Field>::other FieldBlackbox;
     FieldBlackbox Ap (F, A.rowdim(), A.coldim());
     MatrixHom::map (Ap,A,F);
     Element d = detin (Ap);
     return d;
     // Ap is destructed at the end of this block