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// Copyright © 2026 Mikhail Hogrefe
//
// 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::{ModPowerOf2Neg, ModPowerOf2NegAssign};
use crate::num::basic::unsigneds::PrimitiveUnsigned;
fn mod_power_of_2_neg<T: PrimitiveUnsigned>(x: T, pow: u64) -> T {
assert!(pow <= T::WIDTH);
assert!(
x.significant_bits() <= pow,
"x must be reduced mod 2^pow, but {x} >= 2^{pow}"
);
x.wrapping_neg().mod_power_of_2(pow)
}
fn mod_power_of_2_neg_assign<T: PrimitiveUnsigned>(x: &mut T, pow: u64) {
assert!(pow <= T::WIDTH);
assert!(
x.significant_bits() <= pow,
"x must be reduced mod 2^pow, but {x} >= 2^{pow}"
);
x.wrapping_neg_assign();
x.mod_power_of_2_assign(pow);
}
macro_rules! impl_mod_power_of_2_neg {
($t:ident) => {
impl ModPowerOf2Neg for $t {
type Output = $t;
/// Negates a number modulo another number $2^k$. The input must be already reduced
/// modulo $2^k$.
///
/// $f(x, k) = y$, where $x, y < 2^k$ and $-x \equiv y \mod 2^k$.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Panics
/// Panics if `pow` is greater than `Self::WIDTH` or if `self` is greater than or equal
/// to $2^k$.
///
/// # Examples
/// See [here](super::mod_power_of_2_neg#mod_power_of_2_neg).
#[inline]
fn mod_power_of_2_neg(self, pow: u64) -> $t {
mod_power_of_2_neg(self, pow)
}
}
impl ModPowerOf2NegAssign for $t {
/// Negates a number modulo another number $2^k$, in place. The input must be already
/// reduced modulo $2^k$.
///
/// $x \gets y$, where $x, y < 2^k$ and $-x \equiv y \mod 2^k$.
///
/// # Worst-case complexity
/// Constant time and additional memory.
///
/// # Panics
/// Panics if `pow` is greater than `Self::WIDTH` or if `self` is greater than or equal
/// to $2^k$.
///
/// # Examples
/// See [here](super::mod_power_of_2_neg#mod_power_of_2_neg_assign).
#[inline]
fn mod_power_of_2_neg_assign(&mut self, pow: u64) {
mod_power_of_2_neg_assign(self, pow);
}
}
};
}
apply_to_unsigneds!(impl_mod_power_of_2_neg);