Functional programming: Difference between revisions

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The [[lambda calculus]], developed in the 1930s by [[Alonzo Church]], is a [[formal system]] of [[computation]] built from [[function application]]. In 1937 [[Alan Turing]] proved that the lambda calculus and [[Turing machines]] are equivalent models of computation,<ref>{{cite journal|first=A. M.|last=Turing|doi=10.2307/2268280|title=Computability and λ-definability|year=1937|journal=The Journal of Symbolic Logic|pages=153–163|volume=2|issue=4|publisher=Cambridge University Press|jstor=2268280|s2cid=2317046}}</ref> showing that the lambda calculus is [[Turing complete]]. Lambda calculus forms the basis of all functional programming languages. An equivalent theoretical formulation, [[combinatory logic]], was developed by [[Moses Schönfinkel]] and [[Haskell Curry]] in the 1920s and 1930s.<ref>{{cite book|author1=Haskell Brooks Curry|author2=Robert Feys|title=Combinatory Logic|url=https://archive.org/details/combinatorylogic0002curr|url-access=registration|access-date=10 February 2013|year=1958|publisher=North-Holland Publishing Company}}</ref>

Church later developed a weaker system, the [[simply- typed lambda calculus]], which extended the lambda calculus by assigning a [[data type]] to all terms.<ref>{{cite journal |last1=Church |author-link=Alonzo Church |first1=A. |year=1940 |title=A Formulation of the Simple Theory of Types |journal=Journal of Symbolic Logic |volume=5 |issue=2 |pages=56–68 |doi=10.2307/2266170 |jstor=2266170| s2cid=15889861}}</ref> This forms the basis for statically typed functional programming.

The first [[High-level programming language|high-level]] functional programming language, [[Lisp (programming language)|Lisp]], was developed in the late 1950s for the [[IBM 700/7000 series#Scientific Architecture|IBM 700/7000 series]] of scientific computers by [[John McCarthy (computer scientist)|John McCarthy]] while at [[Massachusetts Institute of Technology]] (MIT).<ref>{{cite conference |first=John |last=McCarthy |author-link=John McCarthy (computer scientist) |title=History of Lisp |journal=History of Programming Languages |pages=173–185 |date=June 1978 |url=http://jmc.stanford.edu/articles/lisp/lisp.pdf|doi=10.1145/800025.808387 |place=Los Angeles, CA}}</ref> Lisp functions were defined using Church's lambda notation, extended with a label construct to allow [[Recursion (computer science)|recursive]] functions.<ref>{{cite journal|author=John McCarthy|author-link=John McCarthy (computer scientist)|title=Recursive functions of symbolic expressions and their computation by machine, Part I.|journal=Communications of the ACM|volume=3|issue=4|year=1960|pages=184–195|url=http://jmc.stanford.edu/articles/recursive/recursive.pdf|publisher=ACM New York, NY, US|doi=10.1145/367177.367199|s2cid=1489409}}</ref> Lisp first introduced many paradigmatic features of functional programming, though early Lisps were [[Programming paradigm#Multi-paradigm|multi-paradigm languages]], and incorporated support for numerous programming styles as new paradigms evolved. Later dialects, such as [[Scheme (programming language)|Scheme]] and [[Clojure]], and offshoots such as [[Dylan (programming language)|Dylan]] and [[Julia (programming language)|Julia]], sought to simplify and rationalise Lisp around a cleanly functional core, while [[Common Lisp]] was designed to preserve and update the paradigmatic features of the numerous older dialects it replaced.<ref>{{cite book|author1=Guy L. Steele |author2=Richard P. Gabriel |title=History of programming languages---II |chapter=The evolution of Lisp |pages= 233–330 |date=February 1996 |url=http://dreamsongs.com/Files/HOPL2-Uncut.pdf |doi= 10.1145/234286.1057818 |isbn=978-0-201-89502-5 |s2cid=47047140}}</ref>