On Mon, Nov 24, 2008 at 6:03 PM, Tim Lahey <[EMAIL PROTECTED]> wrote:
>
> On Nov 24, 2008, at 8:45 PM, William Stein wrote:
>
>>
>> On Mon, Nov 24, 2008 at 4:46 PM, Tim Lahey <[EMAIL PROTECTED]>
>> wrote:
>>>
>>> Hi,
>>>
>>> Is there a specific way to add rules (and apply them) to rewrite
>>> expressions in Sage?
>>>
>>> Such as, log(a)-log(b) = log(a/b)
>>>
>>> I need this (and others) in order to properly compare the integration
>>> results from Sage to the list of integrals I have. I'm trying to put
>>> together a suite of integration tests for both correctness and
>>> timing.
>>
>> I don't know if one can do the above (maybe with pynac it is
>> possible).
>> However, in the meantime could you at least "improperly" compare
>> the results for "pseudo"-correctness by evaluating both answers
>> at a bunch of randomly chosen points and see if they differ by a
>> constant?
>>
>
> I'll check the maxima docs. Unfortunately, at the moment, it doesn't
> look like one can use the new symbolics with the standard (maxima)
> integration.
True.
>
> If I do, I get:
>
> sage: var('x,a,b',ns=1)
> (x, a, b)
> sage: f16 = x/(a*x+b)^3
> sage: f16.integrate(x)
> ---------------------------------------------------------------------------
> AttributeError Traceback (most recent call
> last)
>
> /Users/tjlahey/<ipython console> in <module>()
>
> AttributeError: 'sage.symbolic.expression.Expression' object has no
> attribute 'integrate'
Yep, that's not implemented.
> I can easily run timing comparisons between maxima and FriCAS, but
> because
> of how sympy does things (with its separate variables), I'll have to run
> them separately. Comparing maxima and FriCAS, the timings are pretty
> close on
> both for most of the ones I've tried. A few were much longer in FriCAS.
>
> I have a pretty long list of integrals to go through and I've only
> done 16.
Many thanks for doing this!
William
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