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.
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'
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.
Cheers,
Tim.
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