56-589: [REDACTED] Look up erlang in Wiktionary, the free dictionary. Erlang may refer to: Science and technology [ edit ] Erlang (programming language) , a programming language Erlang (unit) , a unit to measure traffic in telecommunications or other domains Erlang distribution , a probability distribution describing the time between events Places in China [ edit ] Mount Erlang ,
112-532: A P-code machine or virtual machine , that hide even the processor's instruction set . This is the approach followed by many interpreted languages such as AWK , and some languages like Java , which are meant to be compiled into some machine-independent intermediate representation code (such as bytecode ). This arrangement simplifies the task of language implementation and its adaptation to different machines, and improves efficiency of sophisticated language features such as reflective programming . It also allows
168-458: A benchmark with 20 million processes was successfully performed with 64-bit Erlang on a machine with 16 GB random-access memory (RAM; total 800 bytes/process). Erlang has supported symmetric multiprocessing since release R11B of May 2006. While 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
224-629: A hierarchy of runtime systems, with the CPU itself—or actually its logic at the microcode layer or below—acting as the lowest-level runtime system. Some compiled or interpreted languages provide an interface that allows application code to interact directly with the runtime system. An example is the Thread class in the Java language . The class allows code (that is animated by one thread) to do things such as start and stop other threads. Normally, core aspects of
280-438: A language's behavior such as task scheduling and resource management are not accessible in this fashion. Higher-level behaviors implemented by a runtime system may include tasks such as drawing text on the screen or making an Internet connection. It is often the case that operating systems provide these kinds of behaviors as well, and when available, the runtime system is implemented as an abstraction layer that translates
336-1028: A lot of money to build a large scale message handling system that really had to be up all the time, could never afford to go down for years at a time, I would unhesitatingly choose Erlang to build it in. Erlang is the programming language used to code WhatsApp . It is also the language of choice for Ejabberd – an XMPP messaging server. Elixir is a programming language that compiles into BEAM byte code (via Erlang Abstract Format). Since being released as open source, Erlang has been spreading beyond telecoms, establishing itself in other vertical markets such as FinTech, gaming, healthcare, automotive, Internet of Things and blockchain. Apart from WhatsApp, there are other companies listed as Erlang's success stories, including Vocalink (a MasterCard company), Goldman Sachs , Nintendo , AdRoll, Grindr , BT Mobile , Samsung , OpenX , and SITA . A factorial algorithm implemented in Erlang: A tail recursive algorithm that produces
392-410: A mechanism that makes it easy for external processes to monitor for crashes (or hardware failures), rather than an in-process mechanism like exception handling used in many other programming languages. Crashes are reported like other messages, which is the only way processes can communicate with each other, and subprocesses can be spawned cheaply (see below ). The "let it crash" philosophy prefers that
448-418: A module in memory at the same time, and processes can concurrently run code from each. The versions are referred to as the "new" and the "old" version. A process will not move into the new version until it makes an external call to its module. An example of the mechanism of hot code loading: For the second version, we add the possibility to reset the count to zero. Only when receiving a message consisting of
504-911: A mountain in Sichuan Erlang, Susong County , a town in Susong County, Anhui Erlang, Taihe County , a town in Taihe County, Anhui Erlang, Hechuan District , a town in Hechuan District, Chongqing Erlang Subdistrict , Jiulongpo District, Chongqing Erlang station , metro station in Erlang Subdistrict Erlang Township , in Cheng County, Gansu Erlang, Guizhou , a town in Xishui County, Guizhou Erlang, Henan ,
560-518: A new process that takes over the old process's task. The official reference implementation of Erlang uses BEAM . BEAM is included in the official distribution of Erlang, called Erlang/OTP. BEAM executes bytecode which is converted to threaded code at load time. It also includes a native code compiler on most platforms, developed by the High Performance Erlang Project (HiPE) at Uppsala University . Since October 2001
616-411: A number of issues including the management of application memory , how the program accesses variables , mechanisms for passing parameters between procedures , interfacing with the operating system (OS), among others. The compiler makes assumptions depending on the specific runtime system to generate correct code. Typically the runtime system will have some responsibility for setting up and managing
SECTION 10
#1732779534347672-459: A person reading the code of the API that invokes a runtime system would not be able to understand the behavior of the API call just by knowing the language the call was written in. At some point, via some mechanism, the execution model stops being that of the language the call is written in and switches over to being the execution model implemented by the runtime system. For example, the trap instruction
728-408: A process be completely restarted rather than trying to recover from a serious failure. Though it still requires handling of errors, this philosophy results in less code devoted to defensive programming where error-handling code is highly contextual and specific. A typical Erlang application is written in the form of a supervisor tree. This architecture is based on a hierarchy of processes in which
784-424: A program can interact with via a runtime system. One unique application of a runtime environment is its use within an operating system that only allows it to run. In other words, from boot until power-down, the entire OS is dedicated to only the application(s) running within that runtime environment. Any other code that tries to run, or any failures in the application(s), will break the runtime environment. Breaking
840-454: A program: compiling source code to an object file that contains all the functions versus compiling an entire program to an executable binary. The object file will only contain assembly code relevant to the included functions, while the executable binary will contain additional code that implements the runtime environment. The object file, on one hand, may be missing information from the runtime environment that will be resolved by linking . On
896-619: A town in Xiping County, Henan Erlang, Sichuan , a town in Gulin County, Sichuan Erlang railway station , on the Qinghai–Tibet Railway Other uses [ edit ] Agner Krarup Erlang (1878–1929), mathematician and engineer after whom several concepts are named Erlang Shen , a Chinese deity See also [ edit ] Erlangen , Germany Erlanger (disambiguation) Topics referred to by
952-496: Is also the gateway through which a running program interacts with the runtime environment . The runtime environment includes not only accessible state values, but also active entities with which the program can interact during execution. For example, environment variables are features of many operating systems, and are part of the runtime environment; a running program can access them via the runtime system. Likewise, hardware devices such as disks or DVD drives are active entities that
1008-568: Is built out of hundreds of small Erlang processes. It was originally proprietary software within Ericsson , developed by Joe Armstrong , Robert Virding, and Mike Williams in 1986, but was released as free and open-source software in 1998. Erlang/OTP is supported and maintained by the Open Telecom Platform (OTP) product unit at Ericsson . The name Erlang , attributed to Bjarne Däcker, has been presumed by those working on
1064-433: Is different from Wikidata All article disambiguation pages All disambiguation pages Erlang (programming language) Erlang ( / ˈ ɜːr l æ ŋ / UR -lang ) is a general-purpose , concurrent , functional high-level programming language , and a garbage-collected runtime system . The term Erlang is used interchangeably with Erlang/OTP, or Open Telecom Platform (OTP), which consists of
1120-529: Is explicit in Erlang, processes communicate using message passing instead of shared variables, which removes the need for explicit locks (a locking scheme is still used internally by the VM). Inter-process communication works via a shared-nothing asynchronous message passing system: every process has a "mailbox", a queue of messages that have been sent by other processes and not yet consumed. A process uses
1176-399: Is less than Pivot ." ++ is the list concatenation operator. A comparison function can be used for more complicated structures for the sake of readability. The following code would sort lists according to length: A Pivot is taken from the first parameter given to qsort() and the rest of Lists is named Rest . Note that the expression is no different in form from (in
SECTION 20
#17327795343471232-405: Is not named in the first definition of qsort , which deals with the base case of an empty list and thus has no need of this function, let alone a name for it. Erlang has eight primitive data types : And three compound data types: Two forms of syntactic sugar are provided: Erlang has no method to define classes, although there are external libraries available. Erlang is designed with
1288-410: Is one method of switching execution models. This difference is what distinguishes an API-invoked execution model, such as Pthreads, from a usual software library. Both Pthreads calls and software library calls are invoked via an API, but Pthreads behavior cannot be understood in terms of the language of the call. Rather, Pthreads calls bring into play an outside execution model, which is implemented by
1344-429: The receive 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
1400-486: The Fibonacci sequence : Omitting the comments gives a much shorter program. Quicksort in Erlang, using list comprehension : The above example recursively invokes the function qsort until nothing remains to be sorted. The expression [Front || Front <- Rest, Front < Pivot] is a list comprehension , meaning "Construct a list of elements Front such that Front is a member of Rest , and Front
1456-453: The stack and heap , and may include features such as garbage collection , threads or other dynamic features built into the language. Every programming language specifies an execution model , and many implement at least part of that model in a runtime system. One possible definition of runtime system behavior, among others, is "any behavior not directly attributable to the program itself". This definition includes putting parameters onto
1512-551: The AXD301 switch, containing over a million lines of Erlang and reported to achieve a high availability of nine "9"s . In December 1998, the implementation of Erlang was open-sourced and most of the Erlang team resigned to form a new company, Bluetail AB. Ericsson eventually relaxed the ban and re-hired Armstrong in 2004. In 2006, native symmetric multiprocessing support was added to the runtime system and VM. Erlang applications are built of very lightweight Erlang processes in
1568-476: The Erlang runtime system , several ready-to-use components (OTP) mainly written in Erlang, and a set of design principles for Erlang programs. The Erlang runtime system is designed for systems with these traits: The Erlang programming language has immutable data, pattern matching , and functional programming . The sequential subset of the Erlang language supports eager evaluation , single assignment , and dynamic typing . A normal Erlang application
1624-559: The Erlang runtime system. Erlang processes can be seen as "living" objects ( object-oriented programming ), with data encapsulation and message passing , but capable of changing behavior during runtime. The Erlang runtime system provides strict process isolation between Erlang processes (this includes data and garbage collection, separated individually by each Erlang process) and transparent communication between processes (see Location transparency ) on different Erlang nodes (on different hosts). Joe Armstrong, co-inventor of Erlang, summarized
1680-515: The HiPE system is fully integrated in Ericsson's Open Source Erlang/OTP system. It also supports interpreting, directly from source code via abstract syntax tree , via script as of R11B-5 release of Erlang. Erlang supports language-level Dynamic Software Updating . To implement this, code is loaded and managed as "module" units; the module is a compilation unit . The system can keep two versions of
1736-534: The Pthreads runtime system (this runtime system is often the OS kernel). As an extreme example, the physical CPU itself can be viewed as an implementation of the runtime system of a specific assembly language. In this view, the execution model is implemented by the physical CPU and memory systems. As an analogy, runtime systems for higher-level languages are themselves implemented using some other languages. This creates
Erlang - Misplaced Pages Continue
1792-413: The appropriate action to correct the error condition. Erlang's main strength is support for concurrency . It has a small but powerful set of primitives to create processes and communicate among them. Erlang is conceptually similar to the language occam , though it recasts the ideas of communicating sequential processes (CSP) in a functional framework and uses asynchronous message passing. Processes are
1848-411: The atom code_switch will the loop execute an external call to codeswitch/1 ( ?MODULE is a preprocessor macro for the current module). If there is a new version of the counter module in memory, then its codeswitch/1 function will be called. The practice of having a specific entry-point into a new version allows the programmer to transform state to what is needed in the newer version. In the example,
1904-417: The behavior is globally invariant: it holds over all executions. This systematic behavior implements the execution model of the language, as opposed to implementing semantics of the particular program (in which text is directly translated into code that computes results). This separation between the semantics of a particular program and the runtime environment is reflected by the different ways of compiling
1960-466: The built-in support for distributed processes: As the example shows, processes may be created on remote nodes, and communication with them is transparent in the sense that communication with remote processes works exactly as communication with local processes. Concurrency supports the primary method of error-handling in Erlang. When a process crashes, it neatly exits and sends a message to the controlling process which can then take action, such as starting
2016-441: The implementation details of parallel runtime systems. A notable example of a parallel runtime system is Cilk , a popular parallel programming model. The proto-runtime toolkit was created to simplify the creation of parallel runtime systems. In addition to execution model behavior, a runtime system may also perform support services such as type checking , debugging , or code generation and optimization . The runtime system
2072-427: The invocation of the runtime system into an invocation of the operating system. This hides the complexity or variations in the services offered by different operating systems. This also implies that the OS kernel can itself be viewed as a runtime system, and that the set of OS calls that invoke OS behaviors may be viewed as interactions with a runtime system. In the limit, the runtime system may provide services such as
2128-504: The language went from laboratory product to real applications following the collapse of the next-generation AXE telephone exchange named AXE-N in 1995. As a result, Erlang was chosen for the next Asynchronous Transfer Mode (ATM) exchange AXD . In February 1998, Ericsson Radio Systems banned the in-house use of Erlang for new products, citing a preference for non-proprietary languages. The ban caused Armstrong and others to make plans to leave Ericsson. In March 1998 Ericsson announced
2184-449: The language. Erlang, together with libraries and the real-time distributed database Mnesia , forms the OTP collection of libraries. Ericsson and a few other companies support Erlang commercially. Runtime system In computer programming , a runtime system or runtime environment is a sub-system that exists in the computer where a program is created, as well as in the computers where
2240-474: The lifecycle of their child processes, and this includes handling situations in which those child processes crash. Any process can become a supervisor by first spawning a child process, then calling erlang:monitor/2 on that process. If the monitored process then crashes, the supervisor will receive a message containing a tuple whose first member is the atom 'DOWN' . The supervisor is responsible firstly for listening for such messages and secondly, for taking
2296-403: The other hand, the code in the object file still depends on assumptions in the runtime system; for example, a function may read parameters from a particular register or stack location, depending on the calling convention used by the runtime environment. Another example is the case of using an application programming interface (API) to interact with a runtime system. The calls to that API look
Erlang - Misplaced Pages Continue
2352-410: The previous example) except for the use of a comparison function in the last part, saying "Construct a list of elements X such that X is a member of Rest , and Smaller is true", with Smaller being defined earlier as The anonymous function is named Smaller in the parameter list of the second definition of qsort so that it can be referenced by that name within that function. It
2408-413: The primary means to structure an Erlang application. They are neither operating system processes nor threads , but lightweight processes that are scheduled by BEAM. Like operating system processes (but unlike operating system threads), they share no state with each other. The estimated minimal overhead for each is 300 words . Thus, many processes can be created without degrading performance. In 2005,
2464-766: The principles of processes in his PhD thesis : Joe Armstrong remarked in an interview with Rackspace in 2013: "If Java is ' write once, run anywhere ', then Erlang is 'write once, run forever'." In 2014, Ericsson reported Erlang was being used in its support nodes, and in GPRS , 3G and LTE mobile networks worldwide and also by Nortel and Deutsche Telekom . Erlang is used in RabbitMQ . As Tim Bray , director of Web Technologies at Sun Microsystems , expressed in his keynote at O'Reilly Open Source Convention (OSCON) in July 2008: If somebody came to me and wanted to pay me
2520-437: The process stack, create space for local variables, and copy function call parameters onto the top of the stack. There are often no clear criteria for determining which language behaviors are part of the runtime system itself and which can be determined by any particular source program. For example, in C, the setup of the stack is part of the runtime system. It is not determined by the semantics of an individual program because
2576-429: The program is intended to be run. The name comes from the compile time and runtime division from compiled languages , which similarly distinguishes the computer processes involved in the creation of a program (compilation) and its execution in the target machine (the runtime). Most programming languages have some form of runtime system that provides an environment in which programs run. This environment may address
2632-497: The proto-runtime approach. Notable early examples of runtime systems are the interpreters for BASIC and Lisp . These environments also included a garbage collector . Forth is an early example of a language designed to be compiled into intermediate representation code; its runtime system was a virtual machine that interpreted that code. Another popular, if theoretical, example is Donald Knuth 's MIX computer. In C and later languages that supported dynamic memory allocation,
2688-433: The runtime environment in turn breaks the OS, stopping all processing and requiring a reboot. If the boot is from read-only memory, an extremely secure, simple, single-mission system is created. Examples of such directly bundled runtime systems include: The runtime system of the C language is a particular set of instructions inserted by the compiler into the executable image. Among other things, these instructions manage
2744-402: The same as calls to a regular software library , however at some point during the call the execution model changes. The runtime system implements an execution model different from that of the language the library is written in terms of. A person reading the code of a normal library would be able to understand the library's behavior by just knowing the language the library was written in. However,
2800-711: The same program to be executed on any machine without an explicit recompiling step, a feature that has become very important since the proliferation of the World Wide Web . To speed up execution, some runtime systems feature just-in-time compilation to machine code. A modern aspect of runtime systems is parallel execution behaviors, such as the behaviors exhibited by mutex constructs in Pthreads and parallel section constructs in OpenMP . A runtime system with such parallel execution behaviors may be modularized according to
2856-463: The same term [REDACTED] This disambiguation page lists articles associated with the title Erlang . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Erlang&oldid=1206681352 " Categories : Disambiguation pages Disambiguation pages with surname-holder lists Hidden categories: Short description
SECTION 50
#17327795343472912-472: The stack before function calls, parallel execution of related behaviors, and disk I/O . By this definition, essentially every language has a runtime system, including compiled languages , interpreted languages , and embedded domain-specific languages . Even API -invoked standalone execution models, such as Pthreads ( POSIX threads ), have a runtime system that implements the execution model's behavior. Most scholarly papers on runtime systems focus on
2968-425: The state is kept as an integer. In practice, systems are built up using design principles from the Open Telecom Platform, which leads to more code upgradable designs. Successful hot code loading is exacting. Code must be written with care to make use of Erlang's facilities. In 1998, Ericsson released Erlang as free and open-source software to ensure its independence from a single vendor and to increase awareness of
3024-517: The telephony switches (for whom the language was designed) to be a reference to Danish mathematician and engineer Agner Krarup Erlang and a syllabic abbreviation of "Ericsson Language". Erlang was designed with the aim of improving the development of telephony applications. The initial version of Erlang was implemented in Prolog and was influenced by the programming language PLEX used in earlier Ericsson exchanges. By 1988 Erlang had proven that it
3080-428: The top level process is known as a "supervisor". The supervisor then spawns multiple child processes that act either as workers or more, lower level supervisors. Such hierarchies can exist to arbitrary depths and have proven to provide a highly scalable and fault-tolerant environment within which application functionality can be implemented. Within a supervisor tree, all supervisor processes are responsible for managing
3136-547: Was suitable for prototyping telephone exchanges, but the Prolog interpreter was far too slow. One group within Ericsson estimated that it would need to be 40 times faster to be suitable for production use. In 1992, work began on the BEAM virtual machine (VM), which compiles Erlang to C using a mix of natively compiled code and threaded code to strike a balance between performance and disk space. According to co-inventor Joe Armstrong,
#346653