Hi Luis, On 25 Nov., 11:45, luisfe <lftab...@yahoo.es> wrote: > As long as you construct L1 with a specified embedding to K, from a > user point of view you are stating "I am working on this subfield L1 > of K, but I want a subfield representation in terms of powers of > r2_1". In that sense yes, K would be canónical.
Sounds good to me. And I think I know how this could be implemented: The job of finding a canonical common parent is done by sage.categories.pushout.pushout(). It starts with considering the constructions that yield to L1 and L2 - in both cases, one has an AlgebraicExtensionFunctor, say, F1 and F2, starting at the same base ring, QQ. Then, pushout() tries to process F1 and F2 into another construction functor, F, so that F1(QQ) and F2(QQ) both coerce into F(QQ). This can be done by - concatenation of F1 and F2, but the order would not be canonical - merging of F1 and F2, but this is not implemented yet. I believe one could implement a merge of F1 and F2 so that F1.merge(F2) (QQ) yields K in your example above, making an algorithm out of your argument that K really is a canonical parent of L1 and L2. And this would solve the coercion bug you encounter. Cheers, Simon -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
