[sage-devel] Re: https://wiki.sagemath.org/ReleaseTours/sage-9.2

[c.ed...@gmail.com]

Hello,

I'm one of the authors of 30243  on 
the enumeration/manipulation of fully commutative elements in Coxeter 
groups. I'd be happy to add a short section on it under Combinatorics, but 
I'm not sure how to log in to the wiki. The help page says I can use my 
trac account, but I log into trac through Github, and as such I have a 
token instead of a password.

-- Chase

On Wednesday, August 19, 2020 at 3:08:05 PM UTC-6 Matthias Koeppe wrote:

> On Saturday, August 8, 2020 at 11:10:17 AM UTC-7, Matthias Koeppe wrote:
>>
>> Let's prepare the release tour for the upcoming 9.2 release by 
>> collaborative editing.
>>
>> https://wiki.sagemath.org/ReleaseTours/sage-9.2
>>
>
> Could someone contribute a brief exposition of the user-visible changes 
> brought by the updates to Sphinx, IPython, the Jupyter notebook?
>
>
>

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Re: [sage-devel] Re: https://wiki.sagemath.org/ReleaseTours/sage-9.2

[c.ed...@gmail.com]

I just noticed 30243 has been closed but not merged yet; I've gone ahead 
and attached a snippet and an image if you'd like to add it to the release 
tour; it would fit as a subsection under Combinatorics. I'll see about 
getting a legacy trac account in the future. 

Thanks!
-- Chase

On Thursday, August 27, 2020 at 8:04:35 AM UTC-6 dim...@gmail.com wrote:

> On Thu, Aug 27, 2020 at 1:00 PM Samuel Lelievre 
>  wrote: 
> > 
> > We could also decide to migrate the release notes 
> > to the Trac Wiki. Then everyone who can participate 
> > in Trac tickets can also participate in the release notes. 
>
> IMHO we would not want to further tie us up to trac, it's probably 
> inevitable that we'll move somewhere more modern. 
>
> As well, I'd much prefer a Wiki which can be updated via Git. 
>
> Dima 
> > 
> > -- 
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>  
>
>

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== Fully Commutative Elements ==

It is now possible by [[https://trac.sagemath.org/ticket/30243]](30243) to 
enumerate and work with the fully commutative elements of a Coxeter group.
Methods to compute *star operations* and plot the *heaps* of such elements are 
also included.

{{{
#!python
sage: FCA3 = CoxeterGroup(['A', 3]).fully_commutative_elements()
sage: FCA3.category()
Category of finite enumerated sets
sage: FCA3.list()
[[],
 [1],
 [2],
 ...
 [1, 3, 2],
 [1, 2, 3],
 [2, 1, 3, 2]]
sage: FCB8 = CoxeterGroup(['B', 8]).fully_commutative_elements()
sage: len(FCB8)# long time (7 seconds)
14299
sage: FCB6 = CoxeterGroup(['B', 6]).fully_commutative_elements()
sage: w = FCB6([1, 6, 2, 5, 4, 6, 5])
sage: w.coset_decomposition({5, 6})
([6, 5, 6], [1, 2, 4, 5])
sage: w.star_operation({5,6}, 'lower')
[1, 5, 2, 4, 6, 5]
sage: FCB6([3, 2, 4, 3, 1]).plot_heap()
}}}

{{attachment:heap.png}}