Negative digits are generated in the output if the numerator starts or
, which means that:
The strategy here is identical to the one used when we output positive
digits. We require three cases as before, and output either -1,
, or
. The derivations are not given here, but
exactly the same method is used and the results are all of the same
form with a few additions and subtractions swapped, and some minor
sign changes present.