Actor is a concurrent, message-passing programming language used to program systems with many actors, such as video games or distributed systems. Actor is based on the Actor model, a mathematical model of concurrent computation.
Actor was created by Hugh Smith and David Ungar in 1986. It was inspired by the programming language Smalltalk, which Smith and Ungar had used in the early 1980s.
Actor is a statically typed, object-oriented language. It has a small set of core data types and operators, and a simple, powerful object model.
Actor programs are composed of actors, which are objects that communicate with each other by sending and receiving messages. An actor can send a message to another actor by using the ! (bang) operator. For example, the following code sends a message from the actor A to the actor B:
A ! B
When an actor receives a message, it can respond by executing code. The code that an actor executes in response to a message is called a behavior.
Actors can also create new actors. When an actor creates a new actor, it becomes the parent of the new actor. The parent-child relationship between actors is called a hierarchy.
Actors can be organized into hierarchies to create complex systems. For example, a video game might have a hierarchy of actors that represent the game world, the player, the enemy characters, and the objects in the game.
A key feature of Actor is its support for concurrent programming. Concurrent programming is a style of programming in which multiple tasks are executed simultaneously. In Actor, concurrent programming is achieved by using message passing to communicate between actors.
Message passing is a form of inter-process communication (IPC) in which messages are sent between processes. In Actor, message passing is used to communicate between actors.
Message passing has several benefits over other forms of IPC, such as shared memory or locks. First, message passing is asynchronous, which means that the sender and receiver of a message do not need to be synchronized. Second, message passing is non-blocking, which means that the sender does not need to wait for the receiver to process the message before continuing.
Third, message passing is scalable, which means that it can be used to communicate between a large number of processes. fourth, message passing is fault tolerant, which means that it can continue to work even if one or more processes fail.
Actor also has support for distributed programming. In distributed programming, a program is divided into multiple parts that run on different computers. Actor's message-passing mechanism can be used to communicate between these parts.
Actor is a powerful programming language that is well suited for programming complex systems. Its support for concurrent and distributed programming makes it an ideal choice for developing large-scale applications.