Some bug in SymmetricFunctions over QQ['t']

[Xie]

R.<t>=QQ['t']
Sym=SymmetricFunctions(R);
Sym.inject_shorthands();

s([[2],[1]])/2 will cause wrong:

ValueError: 1 is not divisible by 2 

But  s([[2],[1]])*1/2 is   good.

 s([[2],[1]])==s[1].  s[1]/2 is good.  

So, why?

If we work on  SymmetricFunctions(FractionField(R)), s([[2],[1]])/2 will work.

[Vincent Delecroix]

The element constructor looks buggy to me as it stores
coefficients which are not in the base ring

sage: a = s([[2],[1]])
sage: a.coefficients()[0].parent()
Integer Ring

The division that is happening is (Integer 1) / (Integer 2)
which is indeed impossible in the Integer Ring. This
should have been (1 in QQ['t']) / (2 in QQ['t']) which is
possible.

The culprit is the function _from_dict which has a coerce
argument which is set to False by default. It is called when
you perform s([[2],[1]]) bt without changing this default.


The difference with FractionField(R) is that it is a field.
In that case another code path is used to perform the division.

Vincent

[Vincent Delecroix]

I opened the following ticket

https://trac.sagemath.org/ticket/33313

to track and hopefully solve the issue.

Thanks for your report.

Best
Vincent