Dactyloidae iOS initial commit

mobile/ios/ThirdParty/Box/MutableBox.swift

@@ -0,0 +1,27 @@
+//  Copyright (c) 2014 Rob Rix. All rights reserved.
+
+/// Wraps a type `T` in a mutable reference type.
+///
+/// While this, like `Box<T>` could be used to work around limitations of value types, it is much more useful for sharing a single mutable value such that mutations are shared.
+///
+/// As with all mutable state, this should be used carefully, for example as an optimization, rather than a default design choice. Most of the time, `Box<T>` will suffice where any `BoxType` is needed.
+public final class MutableBox<T>: MutableBoxType, CustomStringConvertible {
+	/// Initializes a `MutableBox` with the given value.
+	public init(_ value: T) {
+		self.value = value
+	}
+
+	/// The (mutable) value wrapped by the receiver.
+	public var value: T
+
+	/// Constructs a new MutableBox by transforming `value` by `f`.
+	public func map<U>(_ f: (T) -> U) -> MutableBox<U> {
+		return MutableBox<U>(f(value))
+	}
+
+	// MARK: Printable
+
+	public var description: String {
+		return String(describing: value)
+	}
+}