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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift Async Algorithms open source project
//
// Copyright (c) 2022 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
//
//===----------------------------------------------------------------------===//
extension AsyncSequence where Element: Equatable {
/// Creates an asynchronous sequence that omits repeated elements.
public func removeDuplicates() -> AsyncRemoveDuplicatesSequence<Self> {
AsyncRemoveDuplicatesSequence(self) { lhs, rhs in
lhs == rhs
}
}
}
extension AsyncSequence {
/// Creates an asynchronous sequence that omits repeated elements by testing them with a predicate.
public func removeDuplicates(by predicate: @escaping @Sendable (Element, Element) async -> Bool) -> AsyncRemoveDuplicatesSequence<Self> {
return AsyncRemoveDuplicatesSequence(self, predicate: predicate)
}
/// Creates an asynchronous sequence that omits repeated elements by testing them with an error-throwing predicate.
public func removeDuplicates(by predicate: @escaping @Sendable (Element, Element) async throws -> Bool) -> AsyncThrowingRemoveDuplicatesSequence<Self> {
return AsyncThrowingRemoveDuplicatesSequence(self, predicate: predicate)
}
}
/// An asynchronous sequence that omits repeated elements by testing them with a predicate.
public struct AsyncRemoveDuplicatesSequence<Base: AsyncSequence>: AsyncSequence {
public typealias Element = Base.Element
/// The iterator for an `AsyncRemoveDuplicatesSequence` instance.
public struct Iterator: AsyncIteratorProtocol {
@usableFromInline
var iterator: Base.AsyncIterator
@usableFromInline
let predicate: @Sendable (Element, Element) async -> Bool
@usableFromInline
var last: Element?
@usableFromInline
init(iterator: Base.AsyncIterator, predicate: @escaping @Sendable (Element, Element) async -> Bool) {
self.iterator = iterator
self.predicate = predicate
}
@inlinable
public mutating func next() async rethrows -> Element? {
guard let last = last else {
last = try await iterator.next()
return last
}
while let element = try await iterator.next() {
if await !predicate(last, element) {
self.last = element
return element
}
}
return nil
}
}
@usableFromInline
let base: Base
@usableFromInline
let predicate: @Sendable (Element, Element) async -> Bool
init(_ base: Base, predicate: @escaping @Sendable (Element, Element) async -> Bool) {
self.base = base
self.predicate = predicate
}
@inlinable
public func makeAsyncIterator() -> Iterator {
Iterator(iterator: base.makeAsyncIterator(), predicate: predicate)
}
}
/// An asynchronous sequence that omits repeated elements by testing them with an error-throwing predicate.
public struct AsyncThrowingRemoveDuplicatesSequence<Base: AsyncSequence>: AsyncSequence {
public typealias Element = Base.Element
/// The iterator for an `AsyncThrowingRemoveDuplicatesSequence` instance.
public struct Iterator: AsyncIteratorProtocol {
@usableFromInline
var iterator: Base.AsyncIterator
@usableFromInline
let predicate: @Sendable (Element, Element) async throws -> Bool
@usableFromInline
var last: Element?
@usableFromInline
init(iterator: Base.AsyncIterator, predicate: @escaping @Sendable (Element, Element) async throws -> Bool) {
self.iterator = iterator
self.predicate = predicate
}
@inlinable
public mutating func next() async throws -> Element? {
guard let last = last else {
last = try await iterator.next()
return last
}
while let element = try await iterator.next() {
if try await !predicate(last, element) {
self.last = element
return element
}
}
return nil
}
}
@usableFromInline
let base: Base
@usableFromInline
let predicate: @Sendable (Element, Element) async throws -> Bool
init(_ base: Base, predicate: @escaping @Sendable (Element, Element) async throws -> Bool) {
self.base = base
self.predicate = predicate
}
@inlinable
public func makeAsyncIterator() -> Iterator {
Iterator(iterator: base.makeAsyncIterator(), predicate: predicate)
}
}
extension AsyncRemoveDuplicatesSequence: Sendable where Base: Sendable, Base.Element: Sendable { }
extension AsyncThrowingRemoveDuplicatesSequence: Sendable where Base: Sendable, Base.Element: Sendable { }
@available(*, unavailable)
extension AsyncRemoveDuplicatesSequence.Iterator: Sendable { }
@available(*, unavailable)
extension AsyncThrowingRemoveDuplicatesSequence.Iterator: Sendable { }
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