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