fixed-bigint 0.6.1

Fixed-size big integer implementation for Rust
Documentation 
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//! `const_num_traits::Euclid` / `CheckedEuclid` for `HeaplessBigInt<_, Nct>`.
//!
//! Unsigned: Euclidean div/rem are ordinary div/rem. Nct-only, like the
//! division they build on; `checked_*` return `None` on a zero divisor.

use super::HeaplessBigInt;
use crate::MachineWord;
use const_num_traits::{CarryingMul, CheckedEuclid, Euclid, Nct, Zero};

impl<T, const CAP: usize> Euclid for HeaplessBigInt<T, CAP, Nct>
where
    T: MachineWord + CarryingMul<Unsigned = T, Output = T>,
{
    type Output = Self;
    fn div_euclid(self, v: Self) -> Self {
        self / v
    }
    fn rem_euclid(self, v: Self) -> Self {
        self % v
    }
    fn div_rem_euclid(self, v: Self) -> (Self, Self) {
        self.div_rem(&v)
    }
}

impl<T, const CAP: usize> CheckedEuclid for HeaplessBigInt<T, CAP, Nct>
where
    T: MachineWord + CarryingMul<Unsigned = T, Output = T>,
{
    // Unsigned Euclidean == ordinary; delegate to the inherent checked div/rem
    // so the zero-divisor guard lives in one tested place.
    fn checked_div_euclid(self, v: Self) -> Option<Self> {
        self.checked_div(&v)
    }
    fn checked_rem_euclid(self, v: Self) -> Option<Self> {
        self.checked_rem(&v)
    }
    fn checked_div_rem_euclid(self, v: Self) -> Option<(Self, Self)> {
        if v.is_zero() {
            None
        } else {
            Some(self.div_rem(&v))
        }
    }
}

// `&Self` mirrors so `(&h).div_euclid(&g)` resolves without an explicit copy.
impl<T, const CAP: usize> Euclid for &HeaplessBigInt<T, CAP, Nct>
where
    T: MachineWord + CarryingMul<Unsigned = T, Output = T>,
{
    type Output = HeaplessBigInt<T, CAP, Nct>;
    fn div_euclid(self, v: Self) -> Self::Output {
        <HeaplessBigInt<T, CAP, Nct> as Euclid>::div_euclid(*self, *v)
    }
    fn rem_euclid(self, v: Self) -> Self::Output {
        <HeaplessBigInt<T, CAP, Nct> as Euclid>::rem_euclid(*self, *v)
    }
    fn div_rem_euclid(self, v: Self) -> (Self::Output, Self::Output) {
        <HeaplessBigInt<T, CAP, Nct> as Euclid>::div_rem_euclid(*self, *v)
    }
}

impl<T, const CAP: usize> CheckedEuclid for &HeaplessBigInt<T, CAP, Nct>
where
    T: MachineWord + CarryingMul<Unsigned = T, Output = T>,
{
    fn checked_div_euclid(self, v: Self) -> Option<<Self as Euclid>::Output> {
        <HeaplessBigInt<T, CAP, Nct> as CheckedEuclid>::checked_div_euclid(*self, *v)
    }
    fn checked_rem_euclid(self, v: Self) -> Option<<Self as Euclid>::Output> {
        <HeaplessBigInt<T, CAP, Nct> as CheckedEuclid>::checked_rem_euclid(*self, *v)
    }
    fn checked_div_rem_euclid(
        self,
        v: Self,
    ) -> Option<(<Self as Euclid>::Output, <Self as Euclid>::Output)> {
        <HeaplessBigInt<T, CAP, Nct> as CheckedEuclid>::checked_div_rem_euclid(*self, *v)
    }
}

#[cfg(test)]
mod tests {
    use super::HeaplessBigInt;
    use const_num_traits::{CheckedEuclid, Euclid};

    type H = HeaplessBigInt<u8, 4>;

    #[test]
    fn byref_matches_value() {
        let a = H::from(17u8);
        let b = H::from(5u8);
        assert_eq!(Euclid::div_euclid(&a, &b), Euclid::div_euclid(a, b));
        assert_eq!(Euclid::rem_euclid(&a, &b), Euclid::rem_euclid(a, b));
        assert_eq!(Euclid::div_rem_euclid(&a, &b), Euclid::div_rem_euclid(a, b));
        assert_eq!(
            CheckedEuclid::checked_div_euclid(&a, &b),
            CheckedEuclid::checked_div_euclid(a, b)
        );
        assert_eq!(
            CheckedEuclid::checked_rem_euclid(&a, &b),
            CheckedEuclid::checked_rem_euclid(a, b)
        );
        assert_eq!(
            CheckedEuclid::checked_div_rem_euclid(&a, &b),
            CheckedEuclid::checked_div_rem_euclid(a, b)
        );
    }
}