The main idea of this model is that an actor is able to wait for a message by using two different operations, which try to remove a message from the current actor's mailbox. To do so, a partial function must be given to the operation, that specifies a set of message patterns. These operations are receive and react. An actor can suspend with a full thread stack (receive) or it can suspend with just a continuation closure (react) [2.P]. The first operation of an actor to wait for an message is equal to thread-based programming and the second operation to event-based programming.

 The main idea of this model is that an actor is able to wait for a message by using two different operations, which try to remove a message from the current actor's mailbox. To do so, a partial function must be given to the operation, that specifies a set of message patterns. These operations are receive and react. An actor can suspend with a full thread stack (receive) or it can suspend with just a continuation closure (react) [2.P]. The first operation of an actor to wait for an message is equal to thread-based programming and the second operation to event-based programming.

 receive:         def receive[R](f: PartialFunction[Any, R]): R

 receive:         def receive[R](f: PartialFunction[Any, R]): R

 The current actor's mailbox get scanned and if there is one message which matches one of the patterns declared in the partial function, the message is removed from the mailbox and the partial function is applied to the message, the result is returned. Otherwise the current thread blocks. Thus the receiving actor has the ability to execute normally when receiving a message which matches.  Note that receive retains the complete call stack of the receiving actor; the actor’s behavior is therefore a sequential program which corresponds to thread-based programming [2.P]. \\

 The current actor's mailbox get scanned and if there is one message which matches one of the patterns declared in the partial function, the message is removed from the mailbox and the partial function is applied to the message, the result is returned. Otherwise the current thread blocks. Thus the receiving actor has the ability to execute normally when receiving a message which matches.  Note that receive retains the complete call stack of the receiving actor; the actor’s behavior is therefore a sequential program which corresponds to thread-based programming [2.P]. \\

 react:          

 react:          

 The action which is specified in the partial function is the last code that the current actor executes, if the message is matching. The partial function gets registered by the current actor and the underlying thread gets released. React has the return type Nothing, this means that the method never returns normally. When the actor receives a matching message, the earlier registered partial function gets called and the actor's execution gets continued. The partial function f which corresponds to a set of event handlers [2.P]. \\

 The action which is specified in the partial function is the last code that the current actor executes, if the message is matching. The partial function gets registered by the current actor and the underlying thread gets released. React has the return type Nothing, this means that the method never returns normally. When the actor receives a matching message, the earlier registered partial function gets called and the actor's execution gets continued. The partial function f which corresponds to a set of event handlers [2.P]. \\

 For this implementation multiple acotrs are executed by multiple threads and therefore a thread pool is used. Whenever it is necessary the pool can be re sized, to support the operations of the thread-based and event-based model. If only operations of the event-based model are executed then the thread pool could be fixed. To avoid system-included deadlocks, if some actors use thread-based operations, the thread pool has to grow, because if there are outstanding tasks and every worker thread is occupied by a blocked actor, new threads are necessary. \\

 For this implementation multiple acotrs are executed by multiple threads and therefore a thread pool is used. Whenever it is necessary the pool can be re sized, to support the operations of the thread-based and event-based model. If only operations of the event-based model are executed then the thread pool could be fixed. To avoid system-included deadlocks, if some actors use thread-based operations, the thread pool has to grow, because if there are outstanding tasks and every worker thread is occupied by a blocked actor, new threads are necessary. \\

 Since the communication between actors takes place through asynchronous message passing, asynchronous operations get executed, tasks have to be created and submitted to a thread pool for execution. A new task is created, when an actor spawns a new actor or a message, which enables an actor to continue, is send to an actor which is suspended in a react operation or by calling react, where a message can be immediately removed from the mailbox.\\

 Since the communication between actors takes place through asynchronous message passing, asynchronous operations get executed, tasks have to be created and submitted to a thread pool for execution. A new task is created, when an actor spawns a new actor or a message, which enables an actor to continue, is send to an actor which is suspended in a react operation or by calling react, where a message can be immediately removed from the mailbox.\\

 Event-Based Programming without Inversion of Control - Philipp Haller, Martin Odersky  [IoC]\\

 Event-Based Programming without Inversion of Control - Philipp Haller, Martin Odersky  [IoC]\\

 Scala actors: Unifying thread-based and event-based programming - Philipp Haller, Martin Odersky [2.P]\\

 Scala actors: Unifying thread-based and event-based programming - Philipp Haller, Martin Odersky [2.P]\\