Opa (programming language)

Opa

Paradigm	multi-paradigm: functional, imperative
Developer	MLstate
First appeared	2011
Stable release	1.1.1 (stable) / March 8, 2014; 10 years ago (2014-03-08)[1][2]
Typing discipline	static, strong, inferred
OS	Linux, OS X, Windows
License	MIT License, AGPLv3
Website	opalang.org
Influenced by
OCaml, Erlang, JavaScript

Opa is an open-source programming language for developing scalable web applications.

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 the server and JavaScript on the 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 OWASP conference in 2010,^[6] and the source code was released on GitHub^[7] in June 2011, under a GNU Affero General Public License. Later, the license changed to the MIT license for the framework part (library) and AGPL for the compiler so that applications written in Opa can be released under any license, proprietary or open source.