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// This file is part of helpers4.
// Copyright (C) 2025 baxyz
// SPDX-License-Identifier: LGPL-3.0-or-later
use std::collections::HashSet;
use std::hash::Hash;
/// Returns the elements of `a` that are not in `b`, in `a`'s order.
///
/// Duplicates in `a` are kept: only membership in `b` decides whether an element stays.
///
/// # Arguments
///
/// - `a` - The elements to keep from.
/// - `b` - The elements to remove.
///
/// # Examples
///
/// ```
/// use helpers4::array::difference;
///
/// assert_eq!(difference(&[1, 2, 3, 2], &[2]), vec![1, 3]);
/// assert_eq!(difference(&[1, 1, 2], &[3]), vec![1, 1, 2]);
/// ```
pub fn difference<T: Clone + Eq + Hash>(a: &[T], b: &[T]) -> Vec<T> {
let excluded: HashSet<&T> = b.iter().collect();
a.iter()
.filter(|item| !excluded.contains(item))
.cloned()
.collect()
}
#[cfg(test)]
#[path = "difference.test.rs"]
mod tests;
#[cfg(test)]
#[path = "difference.spec.rs"]
mod spec;