úÎD †    ?A type class for observable objects. A minimal implementation $ implements all of these functions. Get the subject's current value. Update the subject'!s value quietly; should NOT call 3 notifyObservers. Rarely called; usually you want ,  which does notify the subject's observers of the change. Add an observer function. Get the list of observers. 0Update the subject value, and notify observers. !Notify observers that the subject's value has changed. Rarely ' called explicitly: usually called via . :Apply an update function to the subject value, and notify  observers. Add an observer which doesn't care about the subject' s value,  only that it' s changed.    /Threadsafe synchronous Subject implementation. Smart constructor for Sub.         simple-observer-0.0.1Control.ObserverControl.Observer.SynchronousSubjectgetValue setValue' addObserver getObserverssetValuenotifyObservers changeValueaddConstObserverSub createSubSubCvalue observers