Hack (programming language)

Hack
Designed by	Julien Verlaguet, Alok Menghrajani, Drew Paroski, and others
Developer	Meta Platforms
First appeared	2014
Stable release	4.172 / 2 November 2022
Typing discipline	Static, dynamic, weak, gradual
OS	Cross-platform
License	MIT License
Website	hacklang.org
Influenced by
	PHP, OCaml, Java, C#, Scala, Haskell

Hack is a programming language for the HipHop Virtual Machine (HHVM), created by Meta (formerly Facebook) as a dialect of PHP. The language implementation is open-source, licensed under the MIT License.^[2]^[3]^[4]

Hack allows programmers to use both dynamic typing and static typing. This kind of a type system is called gradual typing, which is also implemented in other programming languages such as ActionScript.^[5] Hack's type system allows types to be specified for function arguments, function return values, and class properties; however, types of local variables are always inferred and cannot be specified.^[3]^[6]

^ Bryan O'Sullivan (2014-03-28). "Where Credit Belongs for Hack". Archived from the original on 2021-03-01. Retrieved 2019-02-06.
^ ^a ^b "facebook/hhvm: hhvm / hphp / hack / LICENSE". github.com. Meta Platforms. 2018-04-11. Archived from the original on 2019-01-07. Retrieved 2019-02-06.
^ ^a ^b Josh Lockhart (2014-04-03). "Facebook's Hack, HHVM, and the future of PHP". O'Reilly Media. Archived from the original on 2019-01-07. Retrieved 2019-02-06.
^ Cade Metz (2014-03-20). "Facebook Introduces 'Hack,' the Programming Language of the Future". Wired. Archived from the original on 2014-03-28. Retrieved 2019-02-06.
^ Aseem Rastogi; Avik Chaudhuri; Basil Hosmer (January 2012). "The Ins and Outs of Gradual Type Inference" (PDF). Association for Computing Machinery (ACM). Archived (PDF) from the original on 2017-08-12. Retrieved 2019-02-06.
^ "Hack Manual: Hack and HHVM – Type Annotations". docs.hhvm.com. Archived from the original on 2018-08-02. Retrieved 2019-02-06.