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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::rational_vector::RationalVector;
use core::iter::Sum;
const EMPTY: &str = "cannot sum an empty iterator of vectors: the dimension is unknown";
impl Sum for RationalVector {
/// Adds up all the [`RationalVector`]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_q::rational_vector::RationalVector;
///
/// let vs = ["(1/2, -2, 3)", "(1/3, 5, -1/6)", "(1/6, 0, 1/2)"]
/// .map(|s| RationalVector::from_str(s).unwrap());
/// assert_eq!(
/// RationalVector::sum(vs.into_iter()).to_string(),
/// "(1, 3, 10/3)"
/// );
///
/// let vs = ["(18446744073709551615/2, -1/3)", "(1/2, 1/3)"]
/// .map(|s| RationalVector::from_str(s).unwrap());
/// assert_eq!(
/// RationalVector::sum(vs.into_iter()).to_string(),
/// "(9223372036854775808, 0)"
/// );
/// ```
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 RationalVector {
/// Adds up all the [`RationalVector`]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_q::rational_vector::RationalVector;
///
/// let vs = ["(1/2, -2, 3)", "(1/3, 5, -1/6)", "(1/6, 0, 1/2)"]
/// .map(|s| RationalVector::from_str(s).unwrap());
/// assert_eq!(RationalVector::sum(vs.iter()).to_string(), "(1, 3, 10/3)");
///
/// let vs = ["(18446744073709551615/2, -1/3)", "(1/2, 1/3)"]
/// .map(|s| RationalVector::from_str(s).unwrap());
/// assert_eq!(
/// RationalVector::sum(vs.iter()).to_string(),
/// "(9223372036854775808, 0)"
/// );
/// ```
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
}
}