Erlang (programming language): Difference between revisions

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While [[Thread (computing)|threads]] need external library support in most languages, Erlang provides language-level features to create and manage processes with the goal of simplifying concurrent programming. Though all concurrency is explicit in Erlang, processes communicate using [[message passing]] instead of shared variables, which removes the need for explicit [[Lock (computer science)|locks]] (a locking scheme is still used internally by the VM).<ref>{{cite web |title=Lock-free message queue |url=http://erlang.2086793.n4.nabble.com/Lock-free-message-queue-td2550221.html |access-date=23 December 2013}}</ref>

[[Inter-process communication]] works via a [[Shared shared-nothing architecture|shared-nothing]] [[asynchronous method dispatch|asynchronous]] [[message passing]] system: every process has a "mailbox", a [[queue (data structure)|queue]] of messages that have been sent by other processes and not yet consumed. A process uses the <code>receive</code> primitive to retrieve messages that match desired patterns. A message-handling routine tests messages in turn against each pattern, until one of them matches. When the message is consumed and removed from the mailbox the process resumes execution. A message may comprise any Erlang structure, including primitives (integers, floats, characters, atoms), tuples, lists, and functions.

The code example below shows the built-in support for distributed processes: