poulpy/rns/src/num_bigint.rs

use num_bigint::BigInt;
use num_integer::Integer;
use num_traits::{One, Signed, Zero};

pub trait Div {
    fn div_floor(&self, other: &Self) -> Self;
    fn div_round(&self, other: &Self) -> Self;
}

impl Div for BigInt {
    fn div_floor(&self, other: &Self) -> Self {
        let quo: BigInt = self / other;
        if self.sign() != other.sign() {
            return quo - BigInt::one();
        }
        return quo;
    }

    fn div_round(&self, other: &Self) -> Self {
        let (quo, mut rem) = self.div_rem(other);
        rem <<= 1;
        if rem != BigInt::zero() && &rem.abs() > other {
            if self.sign() == other.sign() {
                return quo + BigInt::one();
            } else {
                return quo - BigInt::one();
            }
        }
        return quo;
    }
}