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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::natural_vector::NaturalVector;
use malachite_base::num::arithmetic::traits::{ModPowerOf2, ModPowerOf2Assign};
impl ModPowerOf2 for NaturalVector {
type Output = Self;
/// Divides every element of a [`NaturalVector`] by $2^k$, keeping the remainders, taking the
/// vector by value.
///
/// The result is reduced modulo $2^k$, which is to say that [`mod_power_of_2_is_reduced`](
/// malachite_base::num::arithmetic::traits::ModPowerOf2IsReduced::mod_power_of_2_is_reduced)
/// returns `true` for it. The dimension is unchanged: unlike a polynomial, a vector keeps the
/// elements that reduce to zero, so $(4, 3)$ modulo 4 is $(0, 3)$.
///
/// A [`Natural`](crate::natural::Natural) element can be larger than any $2^k$, so a large $k$
/// is as meaningful as a small one.
///
/// $$
/// f(v, k) = w, \\quad \text{where} \\quad w_i = v_i - 2^k \left \lfloor \frac{v_i}{2^k}
/// \right \rfloor.
/// $$
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(1)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is the total number of bits of the
/// elements.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::num::arithmetic::traits::ModPowerOf2;
/// use malachite_nz::natural_vector::NaturalVector;
///
/// // Every element is taken modulo 2.
/// assert_eq!(
/// NaturalVector::from_str("(1, 3, 2)")
/// .unwrap()
/// .mod_power_of_2(1)
/// .to_string(),
/// "(1, 1, 0)"
/// );
///
/// // An element that reduces to zero stays, so the dimension is unchanged.
/// assert_eq!(
/// NaturalVector::from_str("(4, 3)")
/// .unwrap()
/// .mod_power_of_2(2)
/// .to_string(),
/// "(0, 3)"
/// );
///
/// // A power too wide for a `u64` still does something here.
/// assert_eq!(
/// NaturalVector::from_str("(340282366920938463463374607431768211457)")
/// .unwrap()
/// .mod_power_of_2(64)
/// .to_string(),
/// "(1)"
/// );
/// ```
#[inline]
fn mod_power_of_2(mut self, pow: u64) -> Self {
self.mod_power_of_2_assign(pow);
self
}
}
impl ModPowerOf2 for &NaturalVector {
type Output = NaturalVector;
/// Divides every element of a [`NaturalVector`] by $2^k$, keeping the remainders, taking the
/// vector by reference.
///
/// See the documentation for the [`ModPowerOf2`] implementation on [`NaturalVector`] for
/// details.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is the total number of bits of the
/// elements.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::num::arithmetic::traits::ModPowerOf2;
/// use malachite_nz::natural_vector::NaturalVector;
///
/// let v = NaturalVector::from_str("(4, 3)").unwrap();
/// assert_eq!((&v).mod_power_of_2(2).to_string(), "(0, 3)");
/// // The vector is left alone.
/// assert_eq!(v.to_string(), "(4, 3)");
/// ```
#[inline]
fn mod_power_of_2(self, pow: u64) -> NaturalVector {
NaturalVector {
elements: self
.elements
.iter()
.map(|x| x.mod_power_of_2(pow))
.collect(),
}
}
}
impl ModPowerOf2Assign for NaturalVector {
/// Divides every element of a [`NaturalVector`] by $2^k$, replacing each element by the
/// remainder.
///
/// See the documentation for the [`ModPowerOf2`] implementation on [`NaturalVector`] for
/// details.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(1)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is the total number of bits of the
/// elements.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::num::arithmetic::traits::ModPowerOf2Assign;
/// use malachite_nz::natural_vector::NaturalVector;
///
/// let mut v = NaturalVector::from_str("(1, 3, 2)").unwrap();
/// v.mod_power_of_2_assign(1);
/// assert_eq!(v.to_string(), "(1, 1, 0)");
///
/// let mut v = NaturalVector::from_str("(4, 3)").unwrap();
/// v.mod_power_of_2_assign(2);
/// assert_eq!(v.to_string(), "(0, 3)");
/// ```
#[inline]
fn mod_power_of_2_assign(&mut self, pow: u64) {
for x in &mut self.elements {
x.mod_power_of_2_assign(pow);
}
}
}