Some new GP features
bnrinit
It is now possible to work with the n-torsion quotient of a ray
class group without computing the full bnrinit (which could
require costly factorization and discrete logarithm) by using
bnrinit(bnf„,n).
? bnf = bnfinit(a^2+47);
? bnr = bnrinit(bnf,77); bnr.cyc
%20 = [120,30,3]
? bnr3 = bnrinit(bnf,77,,3); bnr3.cyc
%21 = [3,3,3]
? bnrclassfield(bnr3)
%22 = [x^3+(-132*a-6171)*x+(5863/2*a+765259/2),
% x^3+(-231/2*a+735/2)*x+(-203/2*a-14749/2),
% x^3+(-6*a+3)*x+(-67/2*a+695/2)]