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Opa (programming language)

From Wikipedia, the free encyclopedia
Opa
Paradigmsmulti-paradigm: functional, imperative
DeveloperMLstate
First appeared2011; 13 years ago (2011)
Stable release
1.1.1 (stable) / March 8, 2014; 10 years ago (2014-03-08)[1][2]
Typing disciplinestatic, strong, inferred
Scopelexical
Implementation languageOCaml, Opa, JavaScript, Shell,C, Standard ML
OSLinux, macOS, Windows
LicenseAGPLv3, MIT
Websiteopalang.org
Influenced by
OCaml, Erlang, JavaScript

Opa is a programming language for developing scalable web applications. It is free and open-source software released under a GNU Affero General Public License (AGPLv3), and an MIT License.

It can be used for both client-side and server-side scripting, where complete programs are written in Opa and subsequently compiled to Node.js on a server and JavaScript on a client, with the compiler automating all communication between the two.[3][4] Opa implements strong, static typing, which can be helpful in protecting against security issues such as SQL injections and cross-site scripting attacks.[5]

The language was first officially presented at the Open Worldwide Application Security Project (OWASP) conference in 2010,[6] and the source code was released on GitHub[7] in June 2011, under a GNU Affero General Public License (AGPL). Later, the license changed to the MIT License for the software framework part (the library) and AGPL for the compiler, so that applications written in Opa can be released under any software license, proprietary or open source.

Design and features

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Opa consists of a web server, a database and distributed execution engine.[8] Code written in Opa is compiled to JavaScript using Node.js on the server side and to JavaScript using jQuery for cross-browser compatibility on the client side.[9] The advantage of the approach compared to certain Rich Internet Application (RIA) platforms is that users are not required to install a plugin in their browser.[10] Opa shares motivations with web frameworks, but takes a different approach.[11] Its designers assert that this helps Opa to avoid many security issues, like SQL injections or cross-site scripting (XSS) attacks.[12]

The core language is functional and has a static type system with type inference. Opa also provides sessions which encapsulate an imperative state and communicate using message passing, similar to Erlang processes. Opa provides many structures or functions that are common in web development, as first-class citizen objects, for instance HTML[13] and parsers, based on parsing expression grammars.[14] Because of this adhesion between the language and web-related concepts, Opa is not intended for non-web applications (for instance desktop applications).[15]

The 0.9.0 release in February 2012 introduced database mapping technology for the non-relational, document-oriented database MongoDB, similar to object-relational mapping.[16][17][18] The 1.1.0 release in February 2013 also added support for PostgreSQL, paving the way for the support of several SQL databases.

Examples

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Hello world

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The traditional "Hello, World!" program, producing a web server that serves a static page with "Hello, web!" as its content, can be written in Opa as:[19] 

Server.start(Server.http,
  { title: "Hello"
  , page: function() { <h1>Hello, web!</h1> }
  }
)

It can be compiled to a stand-alone executable JavaScript file with: 

$ opa hello_web.opa

Running the resulting executable JavaScript file launches the web application: 

$ ./hello_web.js

See also

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  • Ur – a functional language for web development
  • Dart – a JavaScript alternative for web apps
  • Haxe – a similar language for web apps
  • CoffeeScript – a language transcompiled to JavaScript for web apps
  • Dark – a language integrating development and deployment of serverless services

References

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  1. ^ "Release 1.1.1: MLstate/opalang". GitHub. Retrieved 2021-01-29.
  2. ^ "Some great news on Opa". Retrieved 2021-01-29.
  3. ^ Koprowski, Adam (24 February 2012). "Node.js vs. Opa: Web Framework Showdown". developer.com.
  4. ^ Opa supports various server-side backends, Nodejs being the most popular one.
  5. ^ Robertson, William; Giovanni, Vigna (2009). "Static Enforcement of Web Application Integrity Through Strong Typing". SSYM'09 Proceedings of the 18th Conference on USENIX Security Symposium.[permanent dead link]
  6. ^ "OPA: Language Support for a Sane, Safe and Secure Web, at OWASP 2010". OWASP. June 2010.
  7. ^ "GitHub repository". GitHub.
  8. ^ "Opa – The Scalable Open Source Cloud Language". WebAppers. 22 July 2011.
  9. ^ "Interview: François-Régis Sinot on Opa, a Web Development Platform". InfoQ. 7 September 2011.
  10. ^ Neil McAllister (8 September 2011). "Introducing Opa, a Web dev language to rule them all". InfoWorld.
  11. ^ "InfoWorld review: Tools for rapid Web development". InfoWorld. 12 May 2010.
  12. ^ "Auch Opa ist für Cloud-Anwendungen". Heise Online. 29 July 2011.
  13. ^ "Opa – a unified approach to web programming". i-Programmer. 28 August 2011.
  14. ^ Koprowski, Binsztok (2011). "TRX: A Formally Verified Parser Interpreter". Logical Methods in Computer Science.
  15. ^ "Opa, un nouveau langage pour le développement d'applications Web" (in French). LinuxFr. 22 June 2011.
  16. ^ "Hello, database". Opa Documentation. Archived from the original on 2014-01-12. Retrieved 2012-02-22.
  17. ^ "Low-level MongoDB support". Opa Documentation. Archived from the original on 2014-01-12. Retrieved 2012-02-22.
  18. ^ "Programming Opa: Web development, reimagined". Computerworld. 1 February 2012.
  19. ^ Aitken, Alastair (26 July 2011). "Opa, the cloud language – a test drive". Morgan Hill. Archived from the original on 25 September 2011. Retrieved 6 September 2011.

Bibliography

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