Method shrink

ciphercore-base/src/ops/adder.rs:168–181

(&self, overflow_bit: bool)

    }

    fn shrink(&self, overflow_bit: bool) -> Result<CarryNode> {
        let bit_len = self.bit_len()? as i64;

        let next_lvl_bits = if overflow_bit {
            bit_len / 2
        } else {
            (bit_len - 1) / 2
        };
        let use_bits = next_lvl_bits * 2;
        let lower = self.sub_slice(0, use_bits)?;
        let higher = self.sub_slice(1, use_bits)?;

        lower.join(&higher)
    }

    /// assumes `bit_len` is the same for `self` and `rhs`
    fn join(&self, rhs: &Self) -> Result<Self> {