Not really a bug but it is indeed annoying. I provided a fix for this
very specific problem
https://trac.sagemath.org/ticket/24308
And opened an issue for the more general problem of the fact that
quotient rings do not know their characteristic
https://trac.sagemath.org/ticket/24309
Vincent
On 30/11/2017 19:40, 'Peter Mueller' via sage-support wrote:
Is it a bug, or is there a reasonable explanation of the following?
kk.<a,b> = GF(2)[]
k.<y,w> = kk.quo(a^2+a+1)
K.<T> = k[]
for n in [10..32]:
print n, (T*y)^n
0 y*T^10
11 (y + 1)*T^11
12 T^12
13 y*T^13
14 (y + 1)*T^14
15 T^15
16 y*T^16
17 (y + 1)*T^17
18 T^18
19 y*T^19
20 (y + 1)*T^20
21---------------------------------------------------------------------------
NotImplementedError Traceback (most recent call last)
[...]
--> 986 return self.base_ring().characteristic()
987
988 def cyclotomic_polynomial(self, n):
[...]
/home/mueller/local/sage-8.0/local/lib/python2.7/site-packages/sage/rings/quotient_ring.pyc
in characteristic(self)
757 NotImplementedError
758 """
--> 759 raise NotImplementedError
760
761 def defining_ideal(self):
NotImplementedError:
sage:
-- Peter Mueller
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