On 25 September 2014 20:51, kcrisman <kcris...@gmail.com> wrote:
>> >> For Sage, fixing the problem is actually trivial: when the
>> >> hypergeometric
>> >> function is a polynomial (and at least when the inputs are exact),
>> >> don't
>> >> call mpmath; just evaluate the polynomial directly and then call .n()
>> >> on the
>> >> result.
>> >>
>> >
>> > Except then Sage would have to know when it is a polynomial, and
>> > probably we
>> > would need to ask Maxima for that (assuming it knows). So maybe not
>> > completely trivial to make sure it works.
>>
>> It's a polynomial when any of the first parameters is a nonpositive
>> integer.
>>
>
> Is that "if and only if"? That would certainly be convenient.
I believe this is true for the same reason as for the power series
expansion of (1-x)^{-n}, there are rising factorials and these hit
zero if and only if they start at a nonpositive integer. But you
should check the definition of hypergeometric function to be 100%
sure.
John
>
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