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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 containing the elements of this set that do not occur
/// in the given set.
///
/// The result contains elements in the same order they appear in `self`.
///
/// let set: OrderedSet = [1, 2, 3, 4]
/// let other: OrderedSet = [6, 4, 2, 0]
/// set.subtracting(other) // [1, 3]
///
/// - Parameter other: Another set.
///
/// - Returns: A new set.
///
/// - Complexity: Expected to be O(`self.count + other.count`) on average, if
/// `Element` implements high-quality hashing.
@inlinable
@inline(__always)
public __consuming func subtracting(_ other: Self) -> Self {
_subtracting(other)
}
// Generalizations
/// Returns a new set containing the elements of this set that do not occur
/// in the given set.
///
/// The result contains elements in the same order they appear in `self`.
///
/// let set: OrderedSet = [1, 2, 3, 4]
/// let other: OrderedSet = [6, 4, 2, 0]
/// set.subtracting(other.unordered) // [1, 3]
///
/// - Parameter other: Another set.
///
/// - Returns: A new set.
///
/// - Complexity: Expected to be O(`self.count + other.count`) on average, if
/// `Element` implements high-quality hashing.
@inlinable
@inline(__always)
public __consuming func subtracting(_ other: UnorderedView) -> Self {
subtracting(other._base)
}
/// Returns a new set containing the elements of this set that do not occur
/// in the given sequence.
///
/// The result contains elements in the same order they appear in `self`.
///
/// let set: OrderedSet = [1, 2, 3, 4]
/// set.subtracting([6, 4, 2, 0] as Array) // [1, 3]
///
/// - Parameter other: A finite sequence of elements.
///
/// - Returns: A new set.
///
/// - Complexity: Expected to be O(`self.count + other.count`) on average, if
/// `Element` implements high-quality hashing.
@inlinable
@inline(__always)
public __consuming func subtracting(_ other: some Sequence<Element>) -> Self {
_subtracting(other)
}
@inlinable
__consuming func _subtracting(_ other: some Sequence<Element>) -> Self {
guard count > 0 else { return Self() }
return _UnsafeBitSet.withTemporaryBitSet(capacity: count) { difference in
difference.insertAll(upTo: count)
var c = count
for item in other {
if let index = self._find(item).index {
if difference.remove(index) {
c &-= 1
if c == 0 {
return Self()
}
}
}
}
assert(c > 0)
return _extractSubset(using: difference, count: c)
}
}
}
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