On Tuesday, December 15, 2015 at 2:06:44 PM UTC-8, vdelecroix wrote:
>
> Now if I restart a new Sage session and start with a failing maxima
> command then the behavior is different
>
> sage: var('k', 'n')
> sage: sum(binomial(n-k,k), k, 0, n)
> Traceback (most recent call last):
> ...
>
> ValueError: ...
> sage: assumptions()
> []
> sage: bool(n >= 0)
> False
> sage: assume(n, 'integer')
> sage: assumptions()
> [n is integer]
> sage: bool(n >= 0) # WTF!?
> True
> sage: assume(n >= 0)
> Traceback (most recent call last):
> ...
>
I can confirm. This might have to do with the following:
sage: var("n,k");
sage: maxima_calculus("properties(_SAGE_VAR_n);")
[]
sage: sum(binomial(n-k,k), k, 0, n)
ValueError: ...
sage: maxima_calculus("properties(_SAGE_VAR_n);")
[\"databaseinfo\",_SAGE_VAR_n>=g2451]
So something in sage's "sum" command causes maxima to store a property on
"n". It is possible we're triggering an error in maxima here: Maxima does
have a "scoping" system for assumptions that should allow it to temporarily
make assumptions for the benefit of local simplfications and then later
restore the original assumptions database state. It could be that we're
calling code in maxima that should use that machinery but doesn't.
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