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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift Collections open source project
//
// Copyright (c) 2021 - 2024 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
//
//===----------------------------------------------------------------------===//
// `OrderedSet` does not directly conform to `SetAlgebra` because its definition
// of equality conflicts with `SetAlgebra` requirements. However, it still
// implements most `SetAlgebra` requirements (except `insert`, which is replaced
// by `append`).
//
// `OrderedSet` also provides an `unordered` view that explicitly conforms to
// `SetAlgebra`. That view implements `Equatable` by ignoring element order,
// so it can satisfy `SetAlgebra` requirements.
extension OrderedSet {
/// Creates an empty set.
///
/// This initializer is equivalent to initializing with an empty array
/// literal.
///
/// - Complexity: O(1)
@inlinable
public init() {
__storage = nil
_elements = []
}
}
extension OrderedSet {
/// Returns a Boolean value that indicates whether the given element exists
/// in the set.
///
/// - Parameter element: An element to look for in the set.
///
/// - Returns: `true` if `member` exists in the set; otherwise, `false`.
///
/// - Complexity: This operation is expected to perform O(1) comparisons on
/// average, provided that `Element` implements high-quality hashing.
@inlinable
public func contains(_ element: Element) -> Bool {
_find_inlined(element).index != nil
}
}
extension OrderedSet {
/// Removes the given element from the set.
///
/// - Parameter member: The element of the set to remove.
///
/// - Returns: The element equal to `member` if `member` is contained in the
/// set; otherwise, `nil`. In some cases, the returned element may be
/// distinguishable from `member` by identity comparison or some other
/// means.
///
/// - Complexity: O(`count`). Removing an element from the middle of the
/// underlying ordered set needs to rearrange the remaining elements to
/// close the resulting gap.
///
/// Removing the last element only takes (amortized) O(1)
/// hashing/comparisons operations, if `Element` implements high quality
/// hashing.
@inlinable
@discardableResult
public mutating func remove(_ member: Element) -> Element? {
let (idx, bucket) = _find(member)
guard let index = idx else { return nil }
return _removeExistingMember(at: index, in: bucket)
}
}
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