 		}
 	}
 
+	/// Appends `element` onto the `Set`.
 	public mutating func append(element: Element) {
 		insert(element)
 	}


	// MARK: Primitive methods

	public func contains(element: Element) -> Bool {
		return values[element] != nil
	}

	public mutating func insert(element: Element) {
		values[element] = Unit()
	}

	public mutating func remove(element: Element) {
		values.removeValueForKey(element)
	}


	// MARK: Private

	/// The underlying dictionary.
	private var values: [Element: Unit]
}

