docs: public BigInteger floor() {
          /* is already integer: return the numerator
           */
          if (b.compareTo(BigInteger.ONE) == 0) {
              return a;
          } else if (a.compareTo(BigInteger.ZERO) > 0) {
              return a.divide(b);
          } else {
              return a.divide(b).subtract(BigInteger.ONE);
          }
      }