- if not cartesian_product:
- # The field for a cartesian product algebra comes from one
- # of its factors and is the same for all factors, so
- # there's no need to "reapply" it on product algebras.
- if self._matrix_basis_is_cartesian:
- # OK since if n == 0, the basis does not consist of tuples.
- P = basis[0].parent()
- basis = tuple( P(tuple(b_i.change_ring(field) for b_i in b))
- for b in basis )
- else:
- basis = tuple( b.change_ring(field) for b in basis )
-