On Apr 20, 2009, at 12:53 PM, Jason Grout wrote:
> Burcin Erocal wrote:
>> On Sun, 19 Apr 2009 10:34:21 -0700
>> Carl Witty <carl.wi...@gmail.com> wrote:
>>
>>> On Sun, Apr 19, 2009 at 7:44 AM, Maurizio
>>> <maurizio.gran...@gmail.com> wrote:
>>>> Carl, I took advantage of your suggestion, even though I assume I
>>>> can't still go through the whole process with the current gcd
>>>> capabilities in Pynac. But before than that, I'd like to point out
>>>> something strange I did notice, and maybe also Burcin can help with
>>>> that:
>>>>
>>>> reset()
>>>> P.<x,z> = QQ[]
>>>>
>>>> B = x^3 + x
>>>>
>>>> var('x, zs', ns = 1)
>>>> from sage.symbolic.ring import NSR
>>>> Bs = NSR(B)
>>>> Bs
>>>> x^3 + x
>>>> Bs.diff(x)
>>>> 0
>>>>
>>>> So, the derivative is not working. Which is the cause? It seems
>>>> that
>>>> the "x" in Bs is not the "x" I declared, so the derivative gets 0
>>>> as a result. Which is the reason?
>>> Looks like a bug to me.
>>>
>>> Burcin, any comments?
>>
>> I agree that it's confusing, but it's not a bug.
>>
>> The command
>>
>> sage: Bs = NSR(B)
>>
>> converts the polynomial B = x^3 + x in QQ[x] to a symbolic
>> expression,
>> with one numeric coefficient, namely B.
>
>
> So is this what happens anytime you do NSR(sage_object)? It
> converts it
> to a constant (as far as symbolics is concerned) with a coefficient of
> sage_object? Or are there any exceptions?
I consider this bad behavior as well. Perhaps it should at least try
to call a _symbolic_ method.
- Robert
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