qfall_math/integer/z/arithmetic/
neg.rs

1// Copyright 2026 Joshua Limbrey
2//
3// This file is part of qFALL-math
4//
5// qFALL-math is free software: you can redistribute it and/or modify it under
6// the terms of the Mozilla Public License Version 2.0 as published by the
7// Mozilla Foundation. See <https://mozilla.org/en-US/MPL/2.0/>.
8
9//! Implementation of the [`Neg`] trait for [`Z`] values.
10
11use super::super::Z;
12use flint3_sys::fmpz_neg;
13use std::ops::Neg;
14
15impl Neg for Z {
16    type Output = Z;
17
18    /// Implements the [`Neg`] trait for [`Z`] values.
19    /// [`Neg`] is implemented for both borrowed and owned [`Z`].
20    ///
21    /// When called on owned [`Z`] it will reuse the memory of `self`.
22    ///
23    /// Returns the additive inverse of `self` as a [`Z`].
24    ///
25    /// # Examples
26    /// ```
27    /// use qfall_math::integer::Z;
28    ///
29    /// let a: Z = Z::from(42);
30    ///
31    /// let b: Z = -&a;
32    /// let c: Z = -a;
33    /// ```
34    fn neg(mut self) -> Self::Output {
35        unsafe { fmpz_neg(&mut self.value, &self.value) };
36        self
37    }
38}
39
40impl Neg for &Z {
41    type Output = Z;
42
43    /// Documentation at [`Z::neg`].
44    fn neg(self) -> Self::Output {
45        let mut out = Z::default();
46        unsafe { fmpz_neg(&mut out.value, &self.value) };
47        out
48    }
49}
50
51#[cfg(test)]
52mod test_neg {
53    use super::Z;
54
55    /// Ensure that `neg` works for small numbers.
56    #[test]
57    fn correct_small() {
58        let a: Z = Z::ONE;
59        let b: Z = Z::MINUS_ONE;
60        let c: Z = Z::ZERO;
61
62        assert_eq!(a, -(-&a));
63        assert_eq!(a, -&b);
64        assert_eq!(b, -&a);
65        assert_eq!(a, -b.clone());
66        assert_eq!(b, -a);
67        assert_eq!(c, -&c);
68        assert_eq!(c.clone(), -c);
69    }
70
71    /// Ensure that `neg` works for large numbers.
72    #[test]
73    fn correct_large() {
74        let a: Z = Z::from(u64::MAX);
75        let b: Z = Z::from(i64::MAX);
76
77        assert_eq!(a, -(-&a));
78        assert_eq!(b, -(-&b));
79    }
80}
qfall_math/integer/z/arithmetic/neg.rs

qfall_math/integer/z/arithmetic/
neg.rs
