malachite_base/num/arithmetic/
mod_power_of_2_abs_squared.rs

1// Copyright © 2026 Mikhail Hogrefe
2//
3// This file is part of Malachite.
4//
5// Malachite is free software: you can redistribute it and/or modify it under the terms of the GNU
6// Lesser General Public License (LGPL) as published by the Free Software Foundation; either version
7// 3 of the License, or (at your option) any later version. See <https://www.gnu.org/licenses/>.
8
9use crate::num::arithmetic::traits::{
10    ModPowerOf2AbsSquared, ModPowerOf2AbsSquaredAssign, ModPowerOf2Square, ModPowerOf2SquareAssign,
11};
12
13macro_rules! impl_mod_power_of_2_abs_squared {
14    ($t:ident) => {
15        impl ModPowerOf2AbsSquared for $t {
16            type Output = $t;
17
18            /// Computes the squared absolute value of a number modulo $2^k$, which for an unsigned
19            /// number is its square modulo $2^k$. The input must be already reduced modulo $2^k$.
20            ///
21            /// $f(x, k) = y$, where $x, y < 2^k$ and $|x|^2 = x^2 \equiv y \mod 2^k$.
22            ///
23            /// # Worst-case complexity
24            /// Constant time and additional memory.
25            ///
26            /// # Panics
27            /// Panics if `pow` is greater than `Self::WIDTH` or if `self` is greater than or equal
28            /// to $2^k$.
29            ///
30            /// # Examples
31            /// See [here](super::mod_power_of_2_abs_squared#mod_power_of_2_abs_squared).
32            #[inline]
33            fn mod_power_of_2_abs_squared(self, pow: u64) -> $t {
34                self.mod_power_of_2_square(pow)
35            }
36        }
37
38        impl ModPowerOf2AbsSquaredAssign for $t {
39            /// Replaces a number with its squared absolute value modulo $2^k$, which for an
40            /// unsigned number is its square modulo $2^k$. The input must be already reduced modulo
41            /// $2^k$.
42            ///
43            /// $x \gets y$, where $x, y < 2^k$ and $|x|^2 = x^2 \equiv y \mod 2^k$.
44            ///
45            /// # Worst-case complexity
46            /// Constant time and additional memory.
47            ///
48            /// # Panics
49            /// Panics if `pow` is greater than `Self::WIDTH` or if `self` is greater than or equal
50            /// to $2^k$.
51            ///
52            /// # Examples
53            /// See [here](super::mod_power_of_2_abs_squared#mod_power_of_2_abs_squared_assign).
54            #[inline]
55            fn mod_power_of_2_abs_squared_assign(&mut self, pow: u64) {
56                self.mod_power_of_2_square_assign(pow);
57            }
58        }
59    };
60}
61apply_to_unsigneds!(impl_mod_power_of_2_abs_squared);
malachite_base/num/arithmetic/mod_power_of_2_abs_squared.rs

malachite_base/num/arithmetic/
mod_power_of_2_abs_squared.rs
