On Monday, April 16, 2018 at 3:21:35 PM UTC+2, Dorian Sabaz wrote:
>
> *sage:* p.factor(dontfactor=[k])
>
> 1/2*(pi*n + k*t)/k                       # bad (factors k still: 
> dontfactor not recognized for k), 1/2 factored as should be.
>
> *sage:* p.factor(k)
>
> 1/2*(pi*n + k*t)/k                       # bad (factors k still: 
> dontfactor not recognized for k), 1/2 factored as should be.
>
>
> Should be:
>
>
> 1/2*(pi*n/k + t) or ideally, 1/2*(n*pi/k + t), note the placement of the 
> "n" (yes it is important for non-commutating algebras).
>

The dontfactor issue seems to be a bug, thanks for the report.  By calling 
var() you are using the symbolic expression part of Sage which has a 
different behaviour from what you expect purely algebraically. Moreover you 
cannot expect a certain order of terms in sums or products. No CAS will 
guarantee that the order of n and pi in the symbolic expression 
(n+pi)^2+(pi+n)^3 will stay the same after evaluation, for example. If you 
deal with noncommutativity you need to use a dedicated ring not symbolics, 
see http://doc.sagemath.org/html/en/reference/rings/index.html

Regards, 

-- 
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 https://groups.google.com/group/sage-devel.
For more options, visit https://groups.google.com/d/optout.

Reply via email to