--- Raymond Toy wrote:
> I certainly agree with that! While testing the hypergeometric stuff,
> it asks sometimes is z > 0. If you say yes, it seems that from then
> on z > 0. But it's not in the assume database, so can't really tell.
> It has something to do with the routines calling checksigntm. I
> haven't figured out what it really does.
>
> But it's very annoying, because maxima no longer asks for the sign of
> z, so everytime you need to test for a different case, you need to
> use a different variable.
asksign assertions are indeed placed in the assume database,
they just don't stay there very long. Well, maybe a little
bit too long -- more on that below.
(%i3) facts (initial);
(%o3) []
(%i4) (([a], asksign (a)), print (is (a > 0)), facts (initial));
Is a positive, negative, or zero?
p;
true
(%o4) [a > 0]
(%i5) facts (initial);
(%o5) []
I guess what might be causing trouble in the hypergeometric
code is that variables are identified by name in the database,
so two different local variables z get mixed up.
At present the policy appears to be "keep assertions in db
til we get back to the input prompt", but maybe it should be
something like "keep assertions in db til they go out of
scope" ??
Sorry if I've repeated something that's already obvious,
and hope this helps,
Robert Dodier
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