class FP2Immutable {

  int sgn0() {
    final int sign0 = fp2.getA().parity();
    final int zero0 = fp2.getA().iszilch() ? 1 : 0;
    final int sign1 = fp2.getB().parity();
    return sign0 | (zero0 & sign1);
  }

    FP2Immutable(FP2Immutable fp2Immutable);
    FP2Immutable(FP2 fp2);
    FP2Immutable(FP fpA, FP fpB);
    FP2Immutable(BIG big1, BIG big2);
    FP2Immutable(int c);
    FP2Immutable(String hex1, String hex2);

}