\runiq

\\ compute the frobenius elements attached to the primes over 
\\ p.  pol defines the field, gal is the list of galois automorphisms
\\ output by nfgaloisconj
{
 frob(p,gal,pol)=
   local(ff,ans,i,j,a,v);
   ff=lift(factormod(pol,p));
   ff=ff[,1]~;
   ans=[];
   for(i=1,length(ff),
      v=vector(length(gal),a,Pol(lift(Mod(Vec(lift(Mod(gal[a]-x^p,ff[i]))),p))));
      for(j=1,length(v),
	 if(v[j]==0,ans=concat(ans,[j]))
      );
   );
   return(uniq(vecsort(ans)))
}