Hi Anne, On 27 Mrz., 00:39, Anne Schilling <a...@math.ucdavis.edu> wrote: > Hi Simon, > > I am not sure this is the smallest example, but I get some error messages when > playing with the quotients: > > sage: n=3 > sage: F = FreeAlgebra(ZZ,n,'x',implementation='letterplace')
That's the other restriction (besides homegeneity): The letterplace Gröbnerbase computation works with fields. So, sadly, ZZ is not possible, but it should work with QQ. This is documented in Singular at http://www.singular.uni-kl.de/Manual/3-1-0/sing_425.htm (All algebras are assumed to be associative $K$-algebras for some field $K$.) and in my code as well, namely in the doc string of LetterplaceIdeal ("In the two-sided case over a field, one can compute Groebner bases ..."), and later on it gives an exammple: Also, it is currently not possible to compute a Groebner basis when the base ring is not a field: sage: FZ.<a,b,c> = FreeAlgebra(ZZ, implementation='letterplace') sage: J = FZ*[a^3-b^3]*FZ sage: J.groebner_basis(2) Traceback (most recent call last): ... RuntimeError: Error in Singular function call 'system': system(...) failed I don't know whether that restriction can be lifted, and *if* it is, whether the Singular team is working on it. I guess, what I should do is to test at the beginning of the groebner_basis method whether we have a field, and give a clear error message. Also I should mention that restriction in the doc string of the groebner_basis method. Best regards, Simon -- You received this message because you are subscribed to the Google Groups "sage-combinat-devel" group. To post to this group, send email to sage-combinat-devel@googlegroups.com. To unsubscribe from this group, send email to sage-combinat-devel+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sage-combinat-devel?hl=en.
