On Wednesday, April 16, 2014 4:16:30 PM UTC-7, BJ wrote:
>
> I have the following code, which produces a list of polynomials in the
> infinite number of variables e_0, e_1, ...
>
> M.<e> = InfinitePolynomialRing(QQ, implementation="sparse")
>
> However, I've been having a lot of trouble figuring out how to do
>> substitutions in these polynomial rings in order to get what I want.
>
>
>
I think the following should be the recommended way of doing this, but
currently it doesn't work:
sage: f = e[1]^2+e[2]^3
sage: f.subs({e[1]: 2}) #this doesn't work
4+e_2^3
the following does work:
sage: f(e_1=2)
4+e_2^3
but it's flawed:
sage: f(e_4=2)
KeyError: 'e_4'
The problem seems to be that the standard subs routines expect the parent
to have a finite, predetermined sequence of generators. That's of course
not the case for your rings. I think InfinitePolynomialRing has to override
more of the methods involved.
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