Lisp (programming language)
Lisp (historically LISP, an abbreviation of "list processing") is a family of programming languages with a long history and a distinctive, fully parenthesized prefix notation.[3] Originally specified in the late 1950s, it is the second-oldest high-level programming language still in common use, after Fortran.[4][5] Lisp has changed since its early days, and many dialects have existed over its history. Today, the best-known general-purpose Lisp dialects are Common Lisp, Scheme, Racket, and Clojure.[6][7][8]
"LISP" redirects here. For the speech impediment, see Lisp. For other uses, see Lisp (disambiguation).Paradigm
Steve Russell, Timothy P. Hart, Mike Levin
1960
Lisp was originally created as a practical mathematical notation for computer programs, influenced by (though not originally derived from)[9] the notation of Alonzo Church's lambda calculus. It quickly became a favored programming language for artificial intelligence (AI) research.[10] As one of the earliest programming languages, Lisp pioneered many ideas in computer science, including tree data structures, automatic storage management, dynamic typing, conditionals, higher-order functions, recursion, the self-hosting compiler,[11] and the read–eval–print loop.[12]
The name LISP derives from "LISt Processor".[13] Linked lists are one of Lisp's major data structures, and Lisp source code is made of lists. Thus, Lisp programs can manipulate source code as a data structure, giving rise to the macro systems that allow programmers to create new syntax or new domain-specific languages embedded in Lisp.
The interchangeability of code and data gives Lisp its instantly recognizable syntax. All program code is written as s-expressions, or parenthesized lists. A function call or syntactic form is written as a list with the function or operator's name first, and the arguments following; for instance, a function f that takes three arguments would be called as (f arg1 arg2 arg3).
Paul Graham identifies nine important aspects of Lisp that distinguished it from existing languages like Fortran:[59]
Lisp was the first language where the structure of program code is represented faithfully and directly in a standard data structure—a quality much later dubbed "homoiconicity". Thus, Lisp functions can be manipulated, altered or even created within a Lisp program without lower-level manipulations. This is generally considered one of the main advantages of the language with regard to its expressive power, and makes the language suitable for syntactic macros and meta-circular evaluation.
A conditional using an if–then–else syntax was invented by McCarthy for a chess program written in Fortran. He proposed its inclusion in ALGOL, but it was not made part of the Algol 58 specification. For Lisp, McCarthy used the more general cond-structure.[60] Algol 60 took up if–then–else and popularized it.
Lisp deeply influenced Alan Kay, the leader of the research team that developed Smalltalk at Xerox PARC; and in turn Lisp was influenced by Smalltalk, with later dialects adopting object-oriented programming features (inheritance classes, encapsulating instances, message passing, etc.) in the 1970s. The Flavors object system introduced the concept of multiple inheritance and the mixin. The Common Lisp Object System provides multiple inheritance, multimethods with multiple dispatch, and first-class generic functions, yielding a flexible and powerful form of dynamic dispatch. It has served as the template for many subsequent Lisp (including Scheme) object systems, which are often implemented via a metaobject protocol, a reflective meta-circular design in which the object system is defined in terms of itself: Lisp was only the second language after Smalltalk (and is still one of the very few languages) to possess such a metaobject system. Many years later, Alan Kay suggested that as a result of the confluence of these features, only Smalltalk and Lisp could be regarded as properly conceived object-oriented programming systems.[61]
Lisp introduced the concept of automatic garbage collection, in which the system walks the heap looking for unused memory. Progress in modern sophisticated garbage collection algorithms such as generational garbage collection was stimulated by its use in Lisp.[62]
Edsger W. Dijkstra in his 1972 Turing Award lecture said,
Largely because of its resource requirements with respect to early computing hardware (including early microprocessors), Lisp did not become as popular outside of the AI community as Fortran and the ALGOL-descended C language. Because of its suitability to complex and dynamic applications, Lisp enjoyed some resurgence of popular interest in the 2010s.[64]
Various object systems and models have been built on top of, alongside, or into Lisp, including
Operating systems[edit]
Several operating systems, including language-based systems, are based on Lisp (use Lisp features, conventions, methods, data structures, etc.), or are written in Lisp,[75] including:
Genera, renamed Open Genera,[76] by Symbolics; Medley, written in Interlisp, originally a family of graphical operating systems that ran on Xerox's later Star workstations;[77][78] Mezzano;[79] Interim;[80][81] ChrysaLisp,[82] by developers of Tao Systems' TAOS.[83]