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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 core::iter::Sum;
const EMPTY: &str = "cannot sum an empty iterator of vectors: the dimension is unknown";
impl Sum for NaturalVector {
/// Adds up all the [`NaturalVector`]s in an iterator, entry by entry.
///
/// The vectors must all have the same dimension, which is also the dimension of the sum. Since
/// the dimension of the zero vector cannot be inferred from an empty iterator, an empty
/// iterator panics rather than summing to zero.
///
/// $$
/// f((v_i)_ {i=0}^{n-1}) = \sum_ {i=0}^{n-1} v_i.
/// $$
///
/// # Worst-case complexity
/// $T(n) = O(n^2)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is the total number of bits of the
/// elements of all the vectors.
///
/// # Panics
/// Panics if the iterator is empty or if the vectors do not all have the same dimension.
///
/// # Examples
/// ```
/// use core::iter::Sum;
/// use core::str::FromStr;
/// use malachite_nz::natural_vector::NaturalVector;
///
/// let vs =
/// ["(1, 2, 3)", "(4, 5, 6)", "(7, 8, 9)"].map(|s| NaturalVector::from_str(s).unwrap());
/// assert_eq!(
/// NaturalVector::sum(vs.into_iter()).to_string(),
/// "(12, 15, 18)"
/// );
///
/// let vs = [
/// "(18446744073709551615, 1)",
/// "(18446744073709551615, 1267650600228229401496703205376)",
/// ]
/// .map(|s| NaturalVector::from_str(s).unwrap());
/// assert_eq!(
/// NaturalVector::sum(vs.into_iter()).to_string(),
/// "(36893488147419103230, 1267650600228229401496703205377)"
/// );
/// ```
fn sum<I>(mut xs: I) -> Self
where
I: Iterator<Item = Self>,
{
let mut sum = xs.next().expect(EMPTY);
for v in xs {
sum += v;
}
sum
}
}
impl<'a> Sum<&'a Self> for NaturalVector {
/// Adds up all the [`NaturalVector`]s in an iterator of references, entry by entry.
///
/// The vectors must all have the same dimension, which is also the dimension of the sum. Since
/// the dimension of the zero vector cannot be inferred from an empty iterator, an empty
/// iterator panics rather than summing to zero.
///
/// $$
/// f((v_i)_ {i=0}^{n-1}) = \sum_ {i=0}^{n-1} v_i.
/// $$
///
/// # Worst-case complexity
/// $T(n) = O(n^2)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is the total number of bits of the
/// elements of all the vectors.
///
/// # Panics
/// Panics if the iterator is empty or if the vectors do not all have the same dimension.
///
/// # Examples
/// ```
/// use core::iter::Sum;
/// use core::str::FromStr;
/// use malachite_nz::natural_vector::NaturalVector;
///
/// let vs =
/// ["(1, 2, 3)", "(4, 5, 6)", "(7, 8, 9)"].map(|s| NaturalVector::from_str(s).unwrap());
/// assert_eq!(NaturalVector::sum(vs.iter()).to_string(), "(12, 15, 18)");
///
/// let vs = [
/// "(18446744073709551615, 1)",
/// "(18446744073709551615, 1267650600228229401496703205376)",
/// ]
/// .map(|s| NaturalVector::from_str(s).unwrap());
/// assert_eq!(
/// NaturalVector::sum(vs.iter()).to_string(),
/// "(36893488147419103230, 1267650600228229401496703205377)"
/// );
/// ```
fn sum<I>(mut xs: I) -> Self
where
I: Iterator<Item = &'a Self>,
{
let mut sum = xs.next().expect(EMPTY).clone();
for v in xs {
sum += v;
}
sum
}
}