Re: int array to poly (libpari)

[Bill Allombert <Bill.Allombert@math.u-bordeaux1.fr>]

On Sun, Apr 10, 2011 at 12:54:57PM +0300, Eugene N wrote:
> Hello
> 
> I am writing some C code, wich will check if a polynomial is irreducible
> (with libpari *gpolisirreducible*).
> 
> Poly will be in the form of int poly[]= {m,m-1,...,0};  (over GF[2])
> 
> I am new to pari, and so far i only have seen *gp_read_str *as means of
> initializing a GEN object from C string.
> 
> But in general, how can i initialize a poly from array?

Read section 4.5.10 of the manual:

The following sample function convert poly to a GEN of type t_POL with 
integers coefficients. You can then use FpX_nbfact(x,gen_2)==1 to check for 
irreducibility modulo 2.

GEN
poly2pari(long m, long *poly)
{
  long l = m+3;
  GEN x = cgetg(l, t_POL);
  x[1] = evalvarn(0);
  for(i=0;i<=m;i++)
    gel(x, i+2) = stoi(i);
  return normalizepol_lg(x, l);
}

Cheers,
Bill.