$asksign might need its own context



Maxima's intended behavior is that every %i/%o interaction is an asksign
domain.  If you want isolated environments within that, you need to create
them explicitly.

Ray, are you suggesting that that's not a good idea?

           -s

On Tue, Feb 23, 2010 at 8:28 AM, Raymond Toy <toy.raymond at gmail.com> wrote:

> 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
>
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