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    use core::num::Wrapping;
    use core::ops::{Add, Mul};

    /// Defines an additive identity element for `Self`.
    ///
    /// # Laws
    ///
    /// ```{.text}
    /// a + 0 = a       ∀ a ∈ Self
    /// 0 + a = a       ∀ a ∈ Self
    /// ```
    pub trait Zero: Sized + Add<Self, Output = Self> {
        /// Returns the additive identity element of `Self`, `0`.
        /// # Purity
        ///
        /// This function should return the same result at all times regardless of
        /// external mutable state, for example values stored in TLS or in
        /// `static mut`s.
        // This cannot be an associated constant, because of bignums.
        fn zero() -> Self;

        /// Sets `self` to the additive identity element of `Self`, `0`.
        fn set_zero(&mut self) {
            *self = Zero::zero();
        }

        /// Returns `true` if `self` is equal to the additive identity.
        #[inline]
        fn is_zero(&self) -> bool;
    }

    macro_rules! zero_impl {
        ($t:ty, $v:expr) => {
            impl Zero for $t {
                #[inline]
                fn zero() -> $t {
                    $v
                }
                #[inline]
                fn is_zero(&self) -> bool {
                    *self == $v
                }
            }
        };
    }

    zero_impl!(usize, 0);
    zero_impl!(u8, 0);
    zero_impl!(u16, 0);
    zero_impl!(u32, 0);
    zero_impl!(u64, 0);
    #[cfg(has_i128)]
    zero_impl!(u128, 0);

    zero_impl!(isize, 0);
    zero_impl!(i8, 0);
    zero_impl!(i16, 0);
    zero_impl!(i32, 0);
    zero_impl!(i64, 0);
    #[cfg(has_i128)]
    zero_impl!(i128, 0);

    zero_impl!(f32, 0.0);
    zero_impl!(f64, 0.0);

    impl<T: Zero> Zero for Wrapping<T>
    where
        Wrapping<T>: Add<Output = Wrapping<T>>,
    {
        fn is_zero(&self) -> bool {
            self.0.is_zero()
        }

        fn set_zero(&mut self) {
            self.0.set_zero();
        }

        fn zero() -> Self {
            Wrapping(T::zero())
        }
    }

    /// Defines a multiplicative identity element for `Self`.
    ///
    /// # Laws
    ///
    /// ```{.text}
    /// a * 1 = a       ∀ a ∈ Self
    /// 1 * a = a       ∀ a ∈ Self
    /// ```
    pub trait One: Sized + Mul<Self, Output = Self> {
        /// Returns the multiplicative identity element of `Self`, `1`.
        ///
        /// # Purity
        ///
        /// This function should return the same result at all times regardless of
        /// external mutable state, for example values stored in TLS or in
        /// `static mut`s.
        // This cannot be an associated constant, because of bignums.
        fn one() -> Self;

        /// Sets `self` to the multiplicative identity element of `Self`, `1`.
        fn set_one(&mut self) {
            *self = One::one();
        }

        /// Returns `true` if `self` is equal to the multiplicative identity.
        ///
        /// For performance reasons, it's best to implement this manually.
        /// After a semver bump, this method will be required, and the
        /// `where Self: PartialEq` bound will be removed.
        #[inline]
        fn is_one(&self) -> bool
        where
            Self: PartialEq,
        {
            *self == Self::one()
        }
    }

    macro_rules! one_impl {
        ($t:ty, $v:expr) => {
            impl One for $t {
                #[inline]
                fn one() -> $t {
                    $v
                }
                #[inline]
                fn is_one(&self) -> bool {
                    *self == $v
                }
            }
        };
    }

    one_impl!(usize, 1);
    one_impl!(u8, 1);
    one_impl!(u16, 1);
    one_impl!(u32, 1);
    one_impl!(u64, 1);
    #[cfg(has_i128)]
    one_impl!(u128, 1);

    one_impl!(isize, 1);
    one_impl!(i8, 1);
    one_impl!(i16, 1);
    one_impl!(i32, 1);
    one_impl!(i64, 1);
    #[cfg(has_i128)]
    one_impl!(i128, 1);

    one_impl!(f32, 1.0);
    one_impl!(f64, 1.0);

    impl<T: One> One for Wrapping<T>
    where
        Wrapping<T>: Mul<Output = Wrapping<T>>,
    {
        fn set_one(&mut self) {
            self.0.set_one();
        }

        fn one() -> Self {
            Wrapping(T::one())
        }
    }

    // Some helper functions provided for backwards compatibility.

    /// Returns the additive identity, `0`.
    #[inline(always)]
    pub fn zero<T: Zero>() -> T {
        Zero::zero()
    }

    /// Returns the multiplicative identity, `1`.
    #[inline(always)]
    pub fn one<T: One>() -> T {
        One::one()
    }

    #[test]
    fn wrapping_identities() {
        macro_rules! test_wrapping_identities {
            ($($t:ty)+) => {
                $(
                    assert_eq!(zero::<$t>(), zero::<Wrapping<$t>>().0);
                    assert_eq!(one::<$t>(), one::<Wrapping<$t>>().0);
                    assert_eq!((0 as $t).is_zero(), Wrapping(0 as $t).is_zero());
                    assert_eq!((1 as $t).is_zero(), Wrapping(1 as $t).is_zero());
                )+
            };
        }

        test_wrapping_identities!(isize i8 i16 i32 i64 usize u8 u16 u32 u64);
    }

    #[test]
    fn wrapping_is_zero() {
        fn require_zero<T: Zero>(_: &T) {}
        require_zero(&Wrapping(42));
    }
    #[test]
    fn wrapping_is_one() {
        fn require_one<T: One>(_: &T) {}
        require_one(&Wrapping(42));
    }

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