`groebner_basis` of modules and PR #3868

[wdecker]

The new functionality provided by PR #3868 does not (yet) fit with the groebner_basis function. Can someone with knowledge please adjust the groebner_basis function and add an example to the tests?

julia> D, (w, x, y, z) = polynomial_ring(QQ, ["w", "x", "y", "z"]);

julia> C, (s,t) = polynomial_ring(QQ, ["s", "t"]);

julia> T, _ = tensor_product(C, D, use_product_ordering = true);

julia> F = free_module(T, 2);

julia> G = gens(T);

julia> S, _ = sub(F, [G[1]*gens(F)[1]]);

julia> groebner_basis(S); ERROR: type ProdOrdering has no field vars

[ederc]

It looks like when checking for the embedded ring ordering there is no handling of a possible product ordering. This is something @RafaelDavidMohr and I should investigate

[joschmitt]

Fixed by #3873.