Functional programming: Difference between revisions

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It is possible to use a functional style of programming in languages that are not traditionally considered functional languages.<ref>{{cite journal |last=Hartel |first=Pieter |author2=Henk Muller |author3=Hugh Glaser |title=The Functional C experience |journal=Journal of Functional Programming |volume=14 |issue=2 |pages=129–135 |date=March 2004 |url=http://www.ub.utwente.nl/webdocs/ctit/1/00000084.pdf |doi=10.1017/S0956796803004817 |s2cid=32346900 |accessdate=2006-05-28 |archivedate=2011-07-19 |archiveurl=https://web.archive.org/web/20110719201553/http://www.ub.utwente.nl/webdocs/ctit/1/00000084.pdf |url-status=deviated }}; {{cite web |title=Functional programming in Python, Part 3 |url=http://www-128.ibm.com/developerworks/linux/library/l-prog3.html |archive-url=https://web.archive.org/web/20071016124848/http://www-128.ibm.com/developerworks/linux/library/l-prog3.html |archive-date=2007-10-16 |author=David Mertz |access-date=2006-09-17 |work=IBM developerWorks }}([https://web.archive.org/web/20071016124848/http://www-128.ibm.com/developerworks/linux/library/l-prog.html Part 1], [https://web.archive.org/web/20071016124848/http://www-128.ibm.com/developerworks/linux/library/l-prog2.html Part 2])</ref> For example, both [[D (programming language)|D]]<ref>{{cite web |url=http://www.digitalmars.com/d/2.0/function.html#pure-functions |title=Functions&nbsp;— D Programming Language 2.0 |publisher=Digital Mars |date=30 December 2012}}</ref> and [[Fortran 95]]<ref name=fortran95/> explicitly support pure functions.

[[JavaScript]], [[Lua (programming language)|Lua]],<ref>{{cite web|url=http://www.luafaq.org/#T1.2|title=Lua Unofficial FAQ (uFAQ)}}</ref> [[Python (programming language)|Python]] and [[Go (programming language)|Go]]<ref>{{Cite web|title=First-Class Functions in Go - The Go Programming Language|url=https://golang.org/doc/codewalk/functions/|access-date=2021-01-04|website=golang.org}}</ref> had [[First-class function|first class functions]] from their inception.<ref>{{cite web|url=https://brendaneich.com/2008/04/popularity/|first=Brendan|last= Eich|title=Popularity|date=3 April 2008}}</ref> Python had support for "[[anonymous function|lambda]]", "[[Map (higher-order function)|map]]", "[[Fold (higher-order function)|reduce]]", and "[[Filter (higher-order function)|filter]]" in 1994, as well as closures in Python 2.2,<ref>{{cite web |url=http://python-history.blogspot.de/2009/04/origins-of-pythons-functional-features.html |title=Origins of Python's "Functional" Features |last=van Rossum |first=Guido |author-link=Guido van Rossum |date=2009-04-21 |access-date=2012-09-27}}</ref> though Python 3 relegated "reduce" to the <code>functools</code> standard library module.<ref>{{cite web |url=https://docs.python.org/dev/library/functools.html#functools.reduce |title=functools — Higher order functions and operations on callable objects |publisher=Python Software Foundation |date=2011-07-31 |access-date=2011-07-31}}</ref> First-class functions have been introduced into other mainstream languages such as [[Perl]] 5.0 in 1994, [[PHP]] 5.3, [[Visual Basic 9]], [[C Sharp (programming language)|C#]] 3.0, [[C++11]], and [[Kotlin (programming language)|Kotlin]].<ref name=":0"/>{{citation needed|date=April 2015}}

In Perl, [[anonymous function|lambda]], [[Map (higher-order function)|map]], [[Fold (higher-order function)|reduce]], [[Filter (higher-order function)|filter]], and [[Closure (computer science)|closures]] are fully supported and frequently used. The book [[Higher-Order Perl]], released in 2005, was written to provide an expansive guide on using Perl for functional programming.

In PHP, [[anonymous class]]es, [[Closure (computer science)|closures]] and lambdas are fully supported. Libraries and language extensions for immutable data structures are being developed to aid programming in the functional style.