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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::{ModIsReduced, ModSubMul, ModSubMulAssign};
use crate::num::basic::unsigneds::PrimitiveUnsigned;
use crate::unsigned_vector::UnsignedVector;
fn assert_reduced<T: PrimitiveUnsigned>(v: &UnsignedVector<T>, w: &UnsignedVector<T>, c: T, m: T) {
assert_eq!(
v.elements.len(),
w.elements.len(),
"cannot sub-multiply vectors of different dimensions"
);
assert!(
v.mod_is_reduced(&m),
"self must be reduced mod m, but {v} has an element >= {m}"
);
assert!(
w.mod_is_reduced(&m),
"w must be reduced mod m, but {w} has an element >= {m}"
);
assert!(
c.mod_is_reduced(&m),
"c must be reduced mod m, but {c} >= {m}"
);
}
// Subtracts `ys` times `c` from `xs` modulo `m`, in place, for inputs already known to be reduced.
// Like FLINT, this handles `c` equal to 0, 1, and `m - 1` directly, and otherwise computes the data
// for multiplying modulo `m` once and reuses it for every element.
fn mod_sub_mul_assign_unchecked<T: PrimitiveUnsigned>(xs: &mut [T], ys: &[T], c: T, m: T) {
if c == T::ZERO {
return;
}
if c == T::ONE {
for (x, &y) in xs.iter_mut().zip(ys) {
x.mod_sub_assign(y, m);
}
} else if c == m - T::ONE {
for (x, &y) in xs.iter_mut().zip(ys) {
x.mod_add_assign(y, m);
}
} else {
let data = T::precompute_mod_mul_data(&m);
for (x, &y) in xs.iter_mut().zip(ys) {
x.mod_sub_assign(y.mod_mul_precomputed(c, m, &data), m);
}
}
}
impl<T: PrimitiveUnsigned> ModSubMul<Self, T, T> for UnsignedVector<T> {
type Output = Self;
/// Subtracts a scalar multiple of an [`UnsignedVector`] from an [`UnsignedVector`] modulo $m$,
/// taking both vectors by value. The elements and the scalar must already be reduced modulo
/// $m$.
///
/// The operation is taken element by element, so the result has the same dimension as the
/// vectors.
///
/// $$
/// f(v, w, c, m) = (v - cw) \bmod m.
/// $$
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(1)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `self.dimension()`.
///
/// # Panics
/// Panics if `self` and `w` have different dimensions, or if any element of `self` or `w`, or
/// `c`, is greater than or equal to `m`.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::num::arithmetic::traits::ModSubMul;
/// use malachite_base::unsigned_vector::UnsignedVector;
///
/// let v = UnsignedVector::<u8>::from_str("(5, 1, 3)").unwrap();
/// let w = UnsignedVector::<u8>::from_str("(2, 6, 4)").unwrap();
/// assert_eq!(v.mod_sub_mul(w, 3, 7).to_string(), "(6, 4, 5)");
/// ```
#[inline]
fn mod_sub_mul(mut self, w: Self, c: T, m: T) -> Self {
self.mod_sub_mul_assign(&w, c, m);
self
}
}
impl<T: PrimitiveUnsigned> ModSubMul<&Self, T, T> for UnsignedVector<T> {
type Output = Self;
/// Subtracts a scalar multiple of an [`UnsignedVector`] from an [`UnsignedVector`] modulo $m$,
/// taking the first vector by value and the second by reference. The elements and the scalar
/// must already be reduced modulo $m$.
///
/// See the documentation for the [`ModSubMul`] implementation that takes both vectors by value
/// for details.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(1)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `self.dimension()`.
///
/// # Panics
/// Panics if `self` and `w` have different dimensions, or if any element of `self` or `w`, or
/// `c`, is greater than or equal to `m`.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::num::arithmetic::traits::ModSubMul;
/// use malachite_base::unsigned_vector::UnsignedVector;
///
/// let v = UnsignedVector::<u8>::from_str("(5, 1, 3)").unwrap();
/// let w = UnsignedVector::<u8>::from_str("(2, 6, 4)").unwrap();
/// assert_eq!(v.mod_sub_mul(&w, 3, 7).to_string(), "(6, 4, 5)");
/// ```
#[inline]
fn mod_sub_mul(mut self, w: &Self, c: T, m: T) -> Self {
self.mod_sub_mul_assign(w, c, m);
self
}
}
impl<T: PrimitiveUnsigned> ModSubMul<&UnsignedVector<T>, T, T> for &UnsignedVector<T> {
type Output = UnsignedVector<T>;
/// Subtracts a scalar multiple of an [`UnsignedVector`] from an [`UnsignedVector`] modulo $m$,
/// taking both vectors by reference. The elements and the scalar must already be reduced modulo
/// $m$.
///
/// See the documentation for the [`ModSubMul`] implementation that takes both vectors by value
/// for details.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `self.dimension()`.
///
/// # Panics
/// Panics if `self` and `w` have different dimensions, or if any element of `self` or `w`, or
/// `c`, is greater than or equal to `m`.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::num::arithmetic::traits::ModSubMul;
/// use malachite_base::unsigned_vector::UnsignedVector;
///
/// let v = UnsignedVector::<u8>::from_str("(5, 1, 3)").unwrap();
/// let w = UnsignedVector::<u8>::from_str("(2, 6, 4)").unwrap();
/// assert_eq!((&v).mod_sub_mul(&w, 3, 7).to_string(), "(6, 4, 5)");
/// ```
fn mod_sub_mul(self, w: &UnsignedVector<T>, c: T, m: T) -> UnsignedVector<T> {
assert_reduced(self, w, c, m);
let mut elements = self.elements.clone();
mod_sub_mul_assign_unchecked(&mut elements, &w.elements, c, m);
UnsignedVector { elements }
}
}
impl<T: PrimitiveUnsigned> ModSubMulAssign<Self, T, T> for UnsignedVector<T> {
/// Subtracts a scalar multiple of an [`UnsignedVector`] from an [`UnsignedVector`] modulo $m$,
/// in place, taking the vector on the right-hand side by value. The elements and the scalar
/// must already be reduced modulo $m$.
///
/// See the documentation for the [`ModSubMul`] implementation that takes both vectors by value
/// for details.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(1)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `self.dimension()`.
///
/// # Panics
/// Panics if `self` and `w` have different dimensions, or if any element of `self` or `w`, or
/// `c`, is greater than or equal to `m`.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::num::arithmetic::traits::ModSubMulAssign;
/// use malachite_base::unsigned_vector::UnsignedVector;
///
/// let mut v = UnsignedVector::<u8>::from_str("(5, 1, 3)").unwrap();
/// let w = UnsignedVector::<u8>::from_str("(2, 6, 4)").unwrap();
/// v.mod_sub_mul_assign(w, 3, 7);
/// assert_eq!(v.to_string(), "(6, 4, 5)");
/// ```
#[inline]
fn mod_sub_mul_assign(&mut self, w: Self, c: T, m: T) {
self.mod_sub_mul_assign(&w, c, m);
}
}
impl<T: PrimitiveUnsigned> ModSubMulAssign<&Self, T, T> for UnsignedVector<T> {
/// Subtracts a scalar multiple of an [`UnsignedVector`] from an [`UnsignedVector`] modulo $m$,
/// in place, taking the vector on the right-hand side by reference. The elements and the scalar
/// must already be reduced modulo $m$.
///
/// See the documentation for the [`ModSubMul`] implementation that takes both vectors by value
/// for details.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(1)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `self.dimension()`.
///
/// # Panics
/// Panics if `self` and `w` have different dimensions, or if any element of `self` or `w`, or
/// `c`, is greater than or equal to `m`.
///
/// # Examples
/// ```
/// use core::str::FromStr;
/// use malachite_base::num::arithmetic::traits::ModSubMulAssign;
/// use malachite_base::unsigned_vector::UnsignedVector;
///
/// let mut v = UnsignedVector::<u8>::from_str("(5, 1, 3)").unwrap();
/// let w = UnsignedVector::<u8>::from_str("(2, 6, 4)").unwrap();
/// v.mod_sub_mul_assign(&w, 3, 7);
/// assert_eq!(v.to_string(), "(6, 4, 5)");
/// ```
fn mod_sub_mul_assign(&mut self, w: &Self, c: T, m: T) {
assert_reduced(self, w, c, m);
mod_sub_mul_assign_unchecked(&mut self.elements, &w.elements, c, m);
}
}