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// Copyright © 2026 Mikhail Hogrefe
//
// Uses code adopted from the FLINT Library.
//
// Copyright © 2010 William Hart
//
// Copyright © 2021 Fredrik Johansson
//
// This file is part of Malachite.
//
// Malachite is free software: you can redistribute it and/or modify it under the terms of the GNU
// Lesser General Public License (LGPL) as published by the Free Software Foundation; either version
// 3 of the License, or (at your option) any later version. See <https://www.gnu.org/licenses/>.
use crate::num::arithmetic::traits::{ModNeg, ModNegAssign};
use crate::num::basic::unsigneds::PrimitiveUnsigned;
fn mod_neg<T: PrimitiveUnsigned>(x: T, m: T) -> T {
assert!(x < m, "x must be reduced mod m, but {x} >= {m}");
if x == T::ZERO { T::ZERO } else { m - x }
}
fn mod_neg_assign<T: PrimitiveUnsigned>(x: &mut T, m: T) {
assert!(*x < m, "x must be reduced mod m, but {x} >= {m}");
if *x != T::ZERO {
*x = m - *x;
}
}
macro_rules! impl_mod_neg {
($t:ident) => {
impl ModNeg for $t {
type Output = $t;
/// Negates a number modulo another number $m$, in place. The input must be already
/// reduced modulo $m$.
///
/// $f(x, m) = y$, where $x, y < m$ and $-x \equiv y \mod m$.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// See [here](super::mod_neg#mod_neg).
///
/// This is equivalent to `nmod_neg` from `nmod.h`, FLINT 2.7.1.
#[inline]
fn mod_neg(self, m: $t) -> $t {
mod_neg(self, m)
}
}
impl ModNegAssign for $t {
/// Negates a number modulo another number $m$. The input must be already reduced modulo
/// $m$.
///
/// $x \gets y$, where $x, y < m$ and $-x \equiv y \mod m$.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Examples
/// See [here](super::mod_neg#mod_neg_assign).
///
/// This is equivalent to `nmod_neg` from `nmod.h`, FLINT 2.7.1, where the output is
/// assigned to `a`.
#[inline]
fn mod_neg_assign(&mut self, m: $t) {
mod_neg_assign(self, m)
}
}
};
}
apply_to_unsigneds!(impl_mod_neg);