1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
|
// RUN: %target-swift-frontend -typecheck %s -dump-api-path %t.dump
// RUN: diff -u %S/Inputs/dumped_api.swift %t.dump/dump_api.swift
public class _AnyIteratorBase {}
/// An abstract `IteratorProtocol` base class over `T` elements.
///
/// Use this as a `Sequence`'s associated `Iterator` type when you
/// don't want to expose details of the concrete iterator, a subclass.
///
/// It is an error to create instances of `AnyIterator` that are not
/// also instances of an `AnyIterator` subclass.
///
/// See also:
///
/// struct AnySequence<S: Sequence>
/// func anyIterator<I: IteratorProtocol>(base: I) -> AnyIterator<I.Element>
/// func anyIterator<T>(nextImplementation: () -> T?) -> AnyIterator<T>
public class AnyIterator<T> : _AnyIteratorBase, IteratorProtocol {
/// Initialize the instance. May only be called from a subclass
/// initializer.
override public init() {
super.init()
}
/// Advance to the next element and return it, or `nil` if no next
/// element exists.
///
/// Note: subclasses must override this method.
public func next() -> T? {fatalError("abstract")}
}
/// Every `IteratorProtocol` can also be a `Sequence`. Note that
/// traversing the sequence consumes the iterator.
extension AnyIterator : Sequence {
/// Returns `self`.
public func makeIterator() -> AnyIterator { return self }
}
/// Return a `IteratorProtocol` instance that wraps `base` but whose type
/// depends only on the type of `I.Element`.
///
/// Example:
///
/// func countStrings() -> AnyIterator<String> {
/// let lazyStrings = lazy(0..<10).map { String($0) }
///
/// // This is a really complicated type of no interest to our
/// // clients.
/// let g: MapSequenceIterator<RangeIterator<Int>, String>
/// = lazyStrings.makeIterator()
/// return anyIterator(g)
/// }
public func anyIterator<I: IteratorProtocol>(base: I) -> AnyIterator<I.Element> {
return FooIteratorBox(base)
}
public class FooIteratorBox<
Base: IteratorProtocol
> : AnyIterator<Base.Element> {
init(_ base: Base) { self.base = base }
public override func next() -> Base.Element? { return base.next() }
var base: Base
}
|
