On Wed, 8 Dec 2021 at 14:31, Neven Sajko <nsa...@gmail.com> wrote:
>
> Suppose I have code like this:
>
> l := [44, 178, 412, 746, 1168, 1669, 2260, 2941, 3712, 4573, 5524, 6565]
> guess(l).1
>
> Replacing the "guess" with a "guessRat" is essentially the same thing AFAIU.
>
> The above code returns a value of type Expression(Integer) that
> represents (visually, at least) a recurrence relation. The recurrence
> relation obviously defines a rational function, which means the
> operation was technically a success.
>
> The problem is that if I try to convert the Expression to an actual
> rational function in a naive manner, as illustrated in the following,
> the conversion fails:
>
> guess(l).1::Fraction(Polynomial(Integer))
>
> So, how difficult would it be to accomplish what I want, either by
> improving the Guess package or by writing my own code? Note that I am
> able to do the conversion in my head, what I'm asking about is how to
> do it in Fricas, mechanically.
>
> My motivation for this is that I want to do iterative guessing, i.e.
> guess (using GuessInteger) a rational function for each member of a
> List(List(Integer)), and then use GuessPolynomialInteger on the list
> of rational functions.
After reading up on Kernels and Expressions, I feel like it should be
possible to take apart the Expression(Integer) that represents the
recurrence. But it seems that is not possible in that particular case.
Suppose I have the result of some invocation of guess$GuessInteger in
a variable called g. None of these seem to be useful at all, that is I
don't see how to extract the polynomials:
kernels(g.1)
operator(mainKernel(g.1))
argument(mainKernel(g.1))
>From the above I can tell that there's only a single Kernel in the
Expression, and that the Kernel has an operator and two arguments, but
I don't see what to do with them.
Any help?
Thanks,
Neven
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