Hack (programming language): Difference between revisions

{{distinguish|Haxe|Hacker|Security hacker}}

| logo size = x64px100px

| designer = Julien Verlaguet, Alok Menghrajani, Drew Paroski, and others<ref>{{cite web |url=http://www.serpentine.com/blog/2014/03/28/where-credit-belongs-for-hack/ |authorlast1=Bryan O'Sullivan |first1=Bryan |title=Where Credit Belongs for Hack |date=2014-03-28 |access-date=2019-02-06 |archive-date=2021-03-01 |archive-url=https://web.archive.org/web/20210301030703/http://www.serpentine.com/blog/2014/03/28/where-credit-belongs-for-hack/ |url-status=live }}</ref>

| license = [[MIT License|MIT]]<ref name="license">{{cite web

| title = facebook/hhvm: hhvm /, hphp /, hack, / LICENSELicense

| website = githubGitHub.com

| website = {{URL|https://hacklang.org/}}

'''Hack''' is a [[programming language]] for the [[HipHop Virtual Machine]] (HHVM), created by [[Meta Platforms|Meta]] (formerly Facebook) as a dialect of [[PHP]]. The language implementation is [[Open-sourcefree and software|open-source software]], licensed under thean [[MIT License]].<ref name="license" /><ref name="oreilly">{{cite web

| authorlast1 = Josh Lockhart |first1 = Josh

Hack allows programmers to use of both [[dynamic typing]] and [[static typing]]. This kind of a [[type systems|type system]] is called [[gradual typing]], which is also implemented in other programming languages such as [[ActionScript]].<ref>{{cite web

}}</ref> Before the announcement of the new programming language, Facebook had already implemented the code and tested it on a large portionpart of its web site.

Hack is designed to interoperate seamlessly with PHP, which is a widely used open-source [[scripting language]] that has a focus on [[web development]] and can be embedded into [[HTML]]. A majority of valid PHP scripts are also valid in Hack; however, numerousmany less frequently-often used PHP features and language constructs are not supportedunsupported in Hack.<ref name="unsupported">{{cite web

Hack extends the [[type hinting]] available in PHP&nbsp;5 through the introduction of static typing, by adding new type hints (for example, for scalar types such as integer or string), as well as by extending the use of type hints (for example, for class properties or function return values). However, types of local variables cannot be specified.<ref name="hack.annotations" /> Since Hack uses a gradual typing system, in the default mode, type annotations are not mandatory even in places they cannot be inferred; the type system will assume the author is correct and admit the code.<ref>{{cite web

}}</ref>

}}</ref> Code must be placed in an entrypoint function. These are automatically executed if they are in the top-level file, but not if the file is included via <code>include</code>, <code>require</code>, or the autoloader. Like other functions in Hack, the function names must be unique within a project&nbsp; – i.e., projects with multiple entrypoints can not call both be called <code>main</code> :

<syntaxhighlight lang="phpoutput">

{{Reflist|30em}}