On Monday, 7 April 2025 at 16:06:42 UTC+2 Waldek Hebisch wrote:
On Sun, Apr 06, 2025 at 06:38:32PM +0200, Waldek Hebisch wrote:
> On Sun, Apr 06, 2025 at 07:11:03AM -0700, Kurt Pagani wrote:
> > Either my understanding of lquo/rquo (Category XFreeAlgebra) is wrong
or
> > there is a bug in the implementation of these functions in
> > XDistributedPolynomial (XDPOLY).
> >
> > p1:= 3*x*y*x*z --> 3 x y x z
> > lquo(p1,3*x*y) --> 9 x z (expected: x z)
> >
> > I think that by "left simplification" is meant mult by a left
> > inverse/recip, similiar as in group theory, although there is no
leftRecip
> > of 3*x*y in XDPOLY, of course. Am I off the track?
>
> Current definition of 'lquo' looks odd, I have noticed this some
> time ago. OTOH there are some odd looking operations on XFreeAlgebra-s
> which actually make a lot of sense. So, it requires some investigative
> work to decide if this is a bug or an unfortunate name of operation
> needed elsewhere.
A little update: this does not look like a bug, there are two different
implementations in 'xpoly.spad' and similar implementation in
'xlpoly.spad'. There are also similar implementations of 'rquo'.
I do not know why 'lquo' and 'rquo' are defined in this way. One
possible explanation could be that in Lie case there are multiple
possibilities for "base" words and maybe the definition tries do
do something for words expressed in different basis.
Ralf showed me another weird result:
%%% (15) -> lquo(x*y, x*y+x)
(15) 1 + y
AFAICS strange definitions of 'lquo' and 'rquo' are not used by
other code, so in principle we could remove them the reduce
confusion.
Yes, as long as there is no reasonable definition I would advocate for
removal.
--
Waldek Hebisch
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