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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
//
//===----------------------------------------------------------------------===//
#if !COLLECTIONS_SINGLE_MODULE
import InternalCollectionsUtilities
#endif
// `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 {
/// Returns a new set with the elements that are common to both this set and
/// the provided other one, in the order they appear in `self`.
///
/// let set: OrderedSet = [1, 2, 3, 4]
/// let other: OrderedSet = [6, 4, 2, 0]
/// set.intersection(other) // [2, 4]
///
/// The result will only contain instances that were originally in `self`.
/// (This matters if equal members can be distinguished by comparing their
/// identities, or by some other means.)
///
/// - Parameter other: Another set.
///
/// - Returns: A new set.
///
/// - Complexity: Expected to be O(`self.count`) on average, if `Element`
/// implements high-quality hashing.
@inlinable
public __consuming func intersection(_ other: Self) -> Self {
var result = Self()
for item in self {
if other.contains(item) {
result._appendNew(item)
}
}
result._checkInvariants()
return result
}
// Generalizations
/// Returns a new set with the elements that are common to both this set and
/// the provided other one, in the order they appear in `self`.
///
/// let set: OrderedSet = [1, 2, 3, 4]
/// let other: OrderedSet = [6, 4, 2, 0]
/// set.intersection(other) // [2, 4]
///
/// The result will only contain instances that were originally in `self`.
/// (This matters if equal members can be distinguished by comparing their
/// identities, or by some other means.)
///
/// - Parameter other: Another set.
///
/// - Returns: A new set.
///
/// - Complexity: Expected to be O(`self.count`) on average, if `Element`
/// implements high-quality hashing.
@inlinable
@inline(__always)
public __consuming func intersection(_ other: UnorderedView) -> Self {
intersection(other._base)
}
/// Returns a new set with the elements that are common to both this set and
/// the provided sequence, in the order they appear in `self`.
///
/// let set: OrderedSet = [1, 2, 3, 4]
/// set.intersection([6, 4, 2, 0] as Array) // [2, 4]
///
/// The result will only contain instances that were originally in `self`.
/// (This matters if equal members can be distinguished by comparing their
/// identities, or by some other means.)
///
/// - Parameter other: A finite sequence of elements.
///
/// - Returns: A new set.
///
/// - Complexity: Expected to be O(*n*) on average where *n* is the number of
/// elements in `other`, if `Element` implements high-quality hashing.
@inlinable
public __consuming func intersection(
_ other: some Sequence<Element>
) -> Self {
_UnsafeBitSet.withTemporaryBitSet(capacity: self.count) { bitset in
for item in other {
if let index = self._find_inlined(item).index {
bitset.insert(index)
}
}
return self._extractSubset(using: bitset)
}
}
}
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