docs: public org.mariadb.jdbc.internal.com.send.authentication.ed25519.math.GroupElement dbl() {
      switch (this.repr) {
        case P2:
        case P3: // Ignore T for P3 representation
          FieldElement XX, YY, B, A, AA, Yn, Zn;
          XX = this.X.square();
          YY = this.Y.square();
          B = this.Z.squareAndDouble();
          A = this.X.add(this.Y);
          AA = A.square();
          Yn = YY.add(XX);
          Zn = YY.subtract(XX);
          return p1p1(this.curve, AA.subtract(Yn), Yn, Zn, B.subtract(Zn));
        default:
          throw new UnsupportedOperationException();
      }
    }