Diff for Erlang (programming language)

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== Erlang (programming language) ==

'''Erlang''' is a general-purpose, concurrent, functional programming language, as well as a garbage-collected runtime system. It was designed by [[Ericsson]] to support distributed, fault-tolerant, soft-real-time, and non-stop applications. Erlang is known for its lightweight concurrency model based on the [[Actor model]], which allows thousands or even millions of concurrent processes to run efficiently.

The language was originally proprietary, but was released as open source in 1998. It has since gained a strong following outside Ericsson, especially in telecommunications, messaging, and web development. The [[BEAM (virtual machine)|BEAM]] virtual machine, which runs Erlang code, also supports the [[Elixir (programming language)|Elixir]] language.

== History ==

Erlang was developed in the late 1980s at the Ericsson Computer Science Laboratory by [[Joe Armstrong]], [[Robert Virding]], and [[Mike Williams]]. The name is widely believed to be a reference to the Danish mathematician [[Agner Krarup Erlang]] or an abbreviation of "Ericsson Language". The first version was implemented in Prolog, but by 1990 a more efficient virtual machine was designed.

In 1996, Ericsson's [[AXE]] telephone exchanges began using Erlang for new subsystems. The language was open-sourced in 1998 to prevent it from being abandoned when Ericsson discontinued a proprietary version. The [[Open Telecom Platform]] (OTP) middleware library was released alongside the language and became an integral part of the Erlang ecosystem.

== Features ==

* '''Concurrency and distribution''': Erlang processes are isolated and communicate via message passing. The runtime handles scheduling, distribution, and failure detection transparently.
* '''Fault tolerance''': "Let it crash" philosophy, with process supervision trees to restart failed components automatically.
* '''Hot code swapping''': Code can be upgraded without stopping the system, a critical feature for telecommunication switches.
* '''Functional programming''': Immutable data, pattern matching, higher-order functions, and single assignment variables.
* '''Memory management''': Per-process garbage collection minimizes pause times and supports massive concurrency.
* '''OTP framework''': Provides libraries for building robust, distributed systems, including [[gen_server]], [[gen_statem]], and [[supervisor]] behaviours.

== Usage ==

Erlang is used in production systems requiring high availability and concurrency. Notable users include:

* Ericsson for telecom infrastructure
* [[WhatsApp]] for messaging servers
* [[RabbitMQ]] for message queuing
* [[CouchDB]] for document databases
* [[Discord]] for real-time communication services (using Erlang and Elixir)

== See also ==

* [[Elixir (programming language)]]
* [[BEAM (virtual machine)]]
* [[Functional programming]]
* [[Actor model]]

[[Category:Programming languages]]
[[Category:Functional languages]]
[[Category:Concurrent programming languages]]
[[Category:Ericsson software]]