>If you want >to use different term orderings or a localisation, you should construct >a "multivariate polynomial ring with a single variable" (I know, this it >sounds silly and is not obvious).
@Simon As state above, the ordering is _silently_ ignored. Thus it is a bug from my point of view. Eof. Or, did I overlook something? Jakob Am Donnerstag, 19. Februar 2015 19:22:30 UTC+1 schrieb Simon King: > > Hi Enrique, > > On 2015-02-19, Enrique Artal <enriqu...@gmail.com <javascript:>> wrote: > >> > This is not really an issue, the problem is the fact that the=20 > >> function=20 > >> > accept the entry *order* but it ignores it silently.=20 > >> > >> Ahm, why do you think it is ignored?=20 > >> > > I have rechecked that =20 > > *R.<t>=3DPolynomialRing(QQ,order=3D'neglex');(1+t).is_unit()* yields > False > > The problem here is that you are constructing a univariate > polynomial ring, for which Sage does not use Singular. If you want > to use different term orderings or a localisation, you should construct > a "multivariate polynomial ring with a single variable" (I know, this it > sounds silly and is not obvious). > > To do so, you should not only provide the list of generator names (this > is what you implicitly do when you write "R.<t> = ..."), but also the > number of generators. Hence: > > sage: R.<t> = PolynomialRing(QQ, 1, order='negdeglex') > sage: R # Note: It is MULTIvariate > Multivariate Polynomial Ring in t over Rational Field > sage: R.term_order() > Negative degree lexicographic term order > sage: (1+t).is_unit() > True > > in contrast to > sage: R.<t> = PolynomialRing(QQ, order='negdeglex') > sage: R # Note: It is UNIvariate > Univariate Polynomial Ring in t over Rational Field > sage: R.term_order() > Traceback (most recent call last): > ... > AttributeError: ... > > Same for "neglex" (I actually didn't know that this exists, it is not > mentioned in the docstring): > sage: R.<t> = PolynomialRing(QQ, 1, order='neglex') > sage: R.term_order() > Negative lexicographic term order > sage: (1+t).is_unit() > True > > Best regards, > Simon > > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
