private LinearTransformation createInverse() {
      return new RegularLinearTransformation(0.0, x, this);
    }
  }

  private static final class NaNLinearTransformation extends LinearTransformation {

    static final NaNLinearTransformation INSTANCE = new NaNLinearTransformation();

    @Override
    public boolean isVertical() {
      return false;
    }

    @Override
    public boolean isHorizontal() {