Re: Vec() and leading zeros of generating function

[Loïc Grenié <loic.grenie@gmail.com>]

2014-08-16 7:43 GMT+02:00 Kevin Ryde <user42_kevin@yahoo.com.au>:
> Vec() can give terms from a polynomial generating function but it
> doesn't include leading zeros.  Eg.
>
>     Vec(x^2/(1-2*x) + O(x^5))
>     =>
>     [1, 2, 4]
>
> Is there a good way to start from the zero'th term so I would get
>
>     [0, 0, 1, 2, 4]

     There is a genuine problem if your series have negative valuation.
  If your series always have non-negative valuation, you can do:

sertovec(s)=concat(vector(valuation(s,variable(s))),Vec(s))

  and use sertovec instead of Vec. The function is not robust and
  will fail if s has negative valuation.

        Hope this helps,

              Loïc