`algorithms/div/knuth`: Can we re-use `r` here somehow? The problem is we can not just
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On 2022-10-24 @recmo wrote in fb3aa20 “Merge pull request #172 from recmo/div2”:
Can we re-use r here somehow? The problem is we can not just
shift the r or borrow because we need to accurately reproduce
the remainder and carry in the middle of a limb.
let (r, borrow) = r.overflowing_sub(u128::from(borrow));
numerator[j + n - 2] = r.low();
numerator[j + n - 1] = r.high();
borrow
} else {
// OPT: Can we re-use `r` here somehow? The problem is we can not just
// shift the `r` or `borrow` because we need to accurately reproduce
// the remainder and carry in the middle of a limb.
let borrow = submul_nx1(&mut numerator[j..j + n], divisor, q);
let n2 = numerator.get(j + n).copied().unwrap_or_default();
borrow != n2
};