Your suggestion that the two a's are not equal is not very likely to be true. In a given expression I think it is
implied that each variable in listofvars(expr) is single valued. Assuming otherwise would make many expressions
incomprehensible.
Rich
--------------------------------------------------
From: "Raymond Toy" <toy.raymond at gmail.com>
Sent: Tuesday, February 23, 2010 8:28 AM
To: <maxima at math.utexas.edu>
Subject: Re: [Maxima] $asksign might need its own context
> On 2/22/10 5:01 PM, Dieter Kaiser wrote:
>> We have the bug report ID: 932095 - ode2 redundant asksign.
>>
>> At first a more simple example to show the problem:
>>
>> (%i3) integrate(x^a,x)+integrate(x^(a-1),x);
>>
>> Is a+1 zero or nonzero?
>> z;
>>
>> Is a zero or nonzero?
>> n;
>>
>> (%o3) log(x)+x^a/a
>>
>> The problem is that Maxima loses the fact that a+1 = 0.
>>
>>
>>
> [snip implementation details]
>> With this changes we get for the example from above:
>>
>> (%i5) integrate(x^a,x)+integrate(x^(a-1),x);
>>
>> Is a+1 zero or nonzero?
>> z;
>>
>> (%o5) log(x)+x^a/a
>>
>>
> Is this really what we want? Granted, for this example it produces the
> desired result, assuming that the a in both integrals really are the
> same a. I'm not sure this is always true.
>
> I recall when working on hgfred that sometimes hgfred would remember
> certain facts when it asked questions. And these facts would be
> remembered so that I could no longer get hgfred to ask the same question
> so I could select a different answer. I didn't know where the info was
> stored so I ended up using new variables all the time.
>
> Of course, at other times, I wished maxima would remember facts, as you
> show above.
>
> It seems that there may not be one correct answer; it all depends on the
> context. :-)
>
> Ray
>
> _______________________________________________
> Maxima mailing list
> Maxima at math.utexas.edu
> http://www.math.utexas.edu/mailman/listinfo/maxima
>