Add 'submodules/SSignalKit/' from commit '359b2ee7c9f20f99f221f78e307369ef5ad0ece2'

git-subtree-dir: submodules/SSignalKit
git-subtree-mainline: 4459dc5b47
git-subtree-split: 359b2ee7c9

submodules/SSignalKit/SwiftSignalKit/Signal.swift

@@ -0,0 +1,85 @@
+import Foundation
+
+let doNothing: () -> Void = { }
+
+public enum NoValue {
+}
+
+public enum NoError {
+}
+
+public func identity<A>(a: A) -> A {
+    return a
+}
+
+precedencegroup PipeRight {
+    associativity: left
+    higherThan: DefaultPrecedence
+}
+
+infix operator |> : PipeRight
+
+public func |> <T, U>(value: T, function: ((T) -> U)) -> U {
+    return function(value)
+}
+
+private final class SubscriberDisposable<T, E> : Disposable {
+    private let subscriber: Subscriber<T, E>
+    private let disposable: Disposable
+    
+    init(subscriber: Subscriber<T, E>, disposable: Disposable) {
+        self.subscriber = subscriber
+        self.disposable = disposable
+    }
+    
+    func dispose() {
+        subscriber.markTerminatedWithoutDisposal()
+        disposable.dispose()
+    }
+}
+
+public struct Signal<T, E> {
+    private let generator: (Subscriber<T, E>) -> Disposable
+    
+    public init(_ generator: @escaping(Subscriber<T, E>) -> Disposable) {
+        self.generator = generator
+    }
+    
+    public func start(next: ((T) -> Void)! = nil, error: ((E) -> Void)! = nil, completed: (() -> Void)! = nil) -> Disposable {
+        let subscriber = Subscriber<T, E>(next: next, error: error, completed: completed)
+        let disposable = self.generator(subscriber)
+        subscriber.assignDisposable(disposable)
+        return SubscriberDisposable(subscriber: subscriber, disposable: disposable)
+    }
+    
+    public static func single(_ value: T) -> Signal<T, E> {
+        return Signal<T, E> { subscriber in
+            subscriber.putNext(value)
+            subscriber.putCompletion()
+            
+            return EmptyDisposable
+        }
+    }
+    
+    public static func complete() -> Signal<T, E> {
+        return Signal<T, E> { subscriber in
+            subscriber.putCompletion()
+            
+            return EmptyDisposable
+        }
+    }
+    
+    public static func fail(_ error: E) -> Signal<T, E> {
+        return Signal<T, E> { subscriber in
+            subscriber.putError(error)
+            
+            return EmptyDisposable
+        }
+    }
+    
+    public static func never() -> Signal<T, E> {
+        return Signal<T, E> { _ in
+            return EmptyDisposable
+        }
+    }
+}