On 08/03/2010 01:43 AM, Dieter Kaiser wrote:
> Am Montag, den 02.08.2010, 23:39 -0600 schrieb Robert Dodier:
>> On 8/2/10, Paul Bowyer<pbowyer at olynet.com> wrote:
>>
>>> So it looks like there is a partial fix for the bug because 0^0 produces
>>> an error message but when 0^i or when
>>> assume i>= 0 is given followed by 0^i, the error still shows up. Am I
>>> correct in this assumption?
>> I seem to recall from a CVS log message that the 0^foo
>> problem was only partially solved, because it turned out
>> to be more complicated than anticipated.
>> I don't know what are the plans of Dieter Kaiser who was
>> working on it.
> Yes, the problem is partially solved. I had to revert parts because of a
> problem in the the routine timesin. Meanwhile I have solved this problem
> and it seems to work. But as I have posted already we get new problems
> too.
>
> Maxima will handle 0^a like any other symbolic expression. Therefore, we
> get e. g. 0^a-0^a --> 0. We get some more correct results, but we get
> wrong results too.
>
> Furthermore, the initial problem of sum(0^i, i, 0, n) -> 0 is not
> solved. We will get again 0. Perhaps this happens because of a
> simplification like 0^a-0^a --> 0.
>
> We might neglect this problem and commit the code, but we might get more
> subtle problems too. It is always problematic to work on the main
> simplifier.
>
> So, at the moment I do not know what is the best.
>
> Dieter Kaiser
>
>
If I knew how to assist I would, but I do not have the expertise in
mathematics or lisp. I've only glanced at lisp and have no usable
knowledge in it whatsoever. In my programming efforts with java (and C++
in the past) when I'm faced with subtle bugs I just use a debugger to
try to track them down. That's sometimes more difficult than it might
seem. In the cases where I cannot seem to find a problem, I use example
data for which I know what the result should be to try to locate where
my code goes awry (I've written some very subtle bugs which have taken
me days to discover). I have no clue how you would go about it in lisp,
but I imagine the process might be similar.
The most I think I can do from my end with Maxima is to try to report
problems when/if I discover them and rely on your expertise with
mathematics and lisp to correct them. If you have ideas on how I might
assist with this effort (within my very limited abilities), I'm open to
suggestion because I like learning new programming related knowledge.
Thanks for the feedback. I'll try to avoid calculations where this bug
might cause difficulties and wait for notification that it has been solved.
Paul Bowyer