On Wed, Jul 22, 2009 at 12:21 PM, William Stein<wst...@gmail.com> wrote:
>
> On Wed, Jul 22, 2009 at 9:31 AM, Golam Mortuza
> Hossain<gmhoss...@gmail.com> wrote:
>>
>> Hi,
>>
>> On Wed, Jul 22, 2009 at 7:47 AM, Burcin Erocal<bur...@erocal.org> wrote:
>>
>>>> > Inability to substitute the argument of D[] has ensured that
>>>> > I am forced out from using new sage symbolics for my own work.
>>>
>>> As I said above, you could have added a short term workaround for this,
>>> once you start using cython to call pynac internals.
>>
>> As someone said, talk is cheap. FYI, I spent two full days trying to
>> find a work-around that really works. May be I did stupid way but I would
>> like to invite you to substitute f(x^2)=1 in the following simple expression
>> by using any sage algorithm
>>
>> ---------
>> h = f(x^2).diff(x)*(x+1/x)
>>
>> sage: h.subs(f(x^2)==1)
>> 2*(x + 1/x)*x*D[0](f)(x^2)
>>
>> sage: h.subs(f(x^2).diff(x)==0)
>> 2*(x + 1/x)*x*D[0](f)(x^2)
>> ---------
>>
>>> I believe the effort could be better spent fixing the bugs you listed
>>> above.
>>
>> Thanks for letting know your "belief". If Sage development is dictated
>> by someone's belief rather than user's need, then I really shouldn't
>> argue anymore.
>
> No worries. This will get sorted out. Burcin is sharing his opinion,
> but it isn't the law or anything, and Sage development is not done by
> "dictators".
>
> I would like to hear more from other users if anybody else has an opinion.
The second thing works in sympy:
In [7]: h.subs(f(x**2).diff(x), 1)
Out[7]:
1
x + ─
x
the first doesn't:
http://code.google.com/p/sympy/issues/detail?id=1549
and we'll fix it. This should definitely work.
Ondrej
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