History of the Scheme programming language: Difference between revisions

Revision as of 22:35, 27 April 2022

Revision as of 20:25, 29 June 2022

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The first implementation of Lisp was on an [[IBM 704]] by [[Steve Russell (computer scientist)|Steve Russell]], who read McCarthy's paper and coded the eval function he described in machine code. The familiar (but puzzling to newcomers) names [[CAR and CDR]] used in Lisp to describe the head element of a list and its tail, evolved from two [[IBM 704]] assembly language commands: Contents of Address Register and Contents of Decrement Register, each of which returned the contents of a 15-bit register corresponding to segments of a [[36-bit computing|36-bit]] IBM 704 instruction [[word (computer architecture)|word]].

The first complete Lisp compiler, written in Lisp, was implemented in 1962 by Tim Hart and Mike Levin at MIT.<ref name="Levin">{{cite web |url=ftp://publications.ai.mit.edu/ai-publications/pdf/AIM-039.pdf |archive-url=https://web.archive.org/web/20201213195043/ftp://publications.ai.mit.edu/ai-publications/pdf/AIM-039.pdf |url-status=dead |archive-date=2020-12-13 |title=AI Memo 39, The New Compiler |lastlast1=Hart |firstfirst1=Tim |last2=Levin |first2=Mike |access-date=2006-10-13 }}</ref> This compiler introduced the Lisp model of incremental compilation, in which compiled and interpreted functions can intermix freely.

The two variants of Lisp most significant in the development of Scheme were both developed at MIT: LISP 1.5<ref>{{cite book |url=https://archive.org/details/lisp15programmer00john |title=LISP 1.5 Programmer's Manual |publisher=[[MIT Press]] |lastlast1=McCarthy |firstfirst1=John |author-link=John McCarthy (computer scientist) |last2=Abrahams |first2=Paul W. |last3=Edwards |first3=Daniel J. |last4=Hart |first4=Timothy P. |last5=Levin |first5=Michael I. |isbn=978-0-262-13011-0 |year=1985 |url-access=registration }}</ref> developed by McCarthy and others, and [[Maclisp]]<ref>{{cite web |url=http://zane.brouhaha.com/~healyzh/doc/lisp.doc.txt |title=Maclisp Reference Manual |date=March 3, 1979 |archive-url=https://web.archive.org/web/20071214064433/http://zane.brouhaha.com/~healyzh/doc/lisp.doc.txt |archive-date=2007-12-14}}</ref> – developed for MIT's [[Project MAC]], a direct descendant of LISP 1.5. which ran on the PDP-10 and [[Multics]] systems.

Since its inception, Lisp was closely connected with the [[artificial intelligence]] (AI) research community, especially on [[PDP-10]]. The 36-bit word size of the [[PDP-6]] and [[PDP-10]] was influenced by the usefulness of having two Lisp [[18-bit computing|18-bit]] pointers in one word.<ref>{{cite newsgroup |quote=The PDP-6 project started in early 1963, as a [[24-bit computing|24-bit]] machine. It grew to 36 bits for LISP, a design goal. |url=https://groups.google.com/group/alt.folklore.computers/browse_thread/thread/6e5602ce733d0ec/17597705ae289112 |title=The History of TOPS or Life in the Fast ACs |newsgroup=alt.folklore.computers |message-id= [e-mail] |date=18 October 1990 |last=Hurley |first=Peter J.}}</ref>

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In 1971 Sussman, [[Drew McDermott]], and [[Eugene Charniak]] had developed a system called [[Planner (programming language)#Micro-planner implementation|Micro-Planner]] which was a partial and somewhat unsatisfactory implementation of [[Carl Hewitt]]'s ambitious [[Planner (programming language)|Planner]] project. Sussman and Hewitt worked together along with others on Muddle, later renamed [[MDL (programming language)|MDL]], an extended Lisp which formed a component of Hewitt's project. Drew McDermott, and Sussman in 1972 developed the Lisp-based language ''Conniver'', which revised the use of automatic backtracking in Planner which they thought was unproductive. Hewitt was dubious that the "hairy control structure" in Conniver was a solution to the problems with Planner. [[Pat Hayes]] remarked: "Their [Sussman and McDermott] solution, to give the user access to the implementation primitives of Planner, is however, something of a retrograde step (what are Conniver's semantics?)"<ref>{{cite journal |last=Hayes |first=Pat |date=1974 |title=Some Problems and Non-Problems in Representation Theory |journal=Society for the Study of Artificial Intelligence and the Simulation of Behaviour (AISB) }}</ref>

In November 1972, Hewitt and his students invented the [[Actor model]] of computation as a solution to the problems with Planner.<ref name="hewitt1973">{{cite journal |lastlast1=Hewitt |firstfirst1=Carl |author-link=Carl Hewitt |last2=Bishop |first2=Peter |last3=Steiger |first3=Richard |title=A Universal Modular Actor Formalism for Artificial Intelligence |publisher=IJCAI |year=1973}}</ref> A partial implementation of Actors was developed called Planner-73 (later called PLASMA). Steele, then a graduate student at MIT, had been following these developments, and he and Sussman decided to implement a version of the Actor model in their own "tiny Lisp" developed on [[Maclisp]], to understand the model better. Using this basis they then began to develop mechanisms for creating actors and sending messages.<ref name="revisited">{{cite journal

|lastlast1=Sussman |firstfirst1=Gerald Jay |author-link=Gerald Jay Sussman |last2=Steele Jr. |first2=Guy L. |author-link2=Guy L. Steele Jr.

|date = December 1998

|url = http://www.brics.dk/~hosc/local/HOSC-11-4-pp399-404.pdf

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|pages = 399–404

|doi = 10.1023/A:1010079421970

|s2cid=7704398 |issn = 1388-3690

|access-date = 2006-06-19

|url-status = dead

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}}</ref>

PLASMA's use of lexical scope was similar to the [[lambda calculus]]. Sussman and Steele decided to try to model Actors in the lambda calculus. They called their modeling system Schemer, eventually changing it to Scheme to fit the six-character limit on the [[Incompatible Timesharing System|ITS]] file system on their DEC [[PDP-10]]. They soon concluded Actors were essentially closures that never return but instead invoke a [[continuation]], and thus they decided that the closure and the Actor were, for the purposes of their investigation, essentially identical concepts. They eliminated what they regarded as redundant code and, at that point, discovered that they had written a very small and capable dialect of Lisp. Hewitt remained critical of the "hairy control structure" in Scheme<ref>{{cite journal |last=Hewitt |first=Carl |author-link=Carl Hewitt |date=December 1976 |title=Viewing Control Structures as Patterns of Passing Messages |journal=AI Memo 410 }}</ref><ref>{{cite journal |last=Hewitt |first=Carl |author-link=Carl Hewitt |date=June 1977 |title=Viewing Control Structures as Patterns of Passing Messages |journal=Journal of Artificial Intelligence |volume=8 |issue=3 |pages=323–364 |doi=10.1016/0004-3702(77)90033-9 |hdl=1721.1/6272 }}</ref> and considered primitives (e.g., <code>START!PROCESS</code>, <code>STOP!PROCESS</code>, and <code>EVALUATE!UNINTERRUPTIBLY</code>) used in the Scheme implementation to be a backward step.

25 years later, in 1998, Sussman and Steele reflected that the minimalism of Scheme was not a conscious design goal, but rather the unintended outcome of the design process. "We were actually trying to build something complicated and discovered, serendipitously, that we had accidentally designed something that met all our goals but was much simpler than we had intended... we realized that the lambda calculus—a small, simple formalism—could serve as the core of a powerful and expressive programming language."<ref name="revisited"/>

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==Standardization==

The Scheme language is [[Technical standard|standardized]] in the official [[Institute of Electrical and Electronics Engineers]] (IEEE) standard,<ref name="ieee1178">1178-1990 (R1995) IEEE Standard for the Scheme Programming Language</ref> and a de facto standard called the ''Revisedⁿ Report on the Algorithmic Language Scheme'' (R''n''RS). The most widely implemented standard is ''R5RS'' (1998),<ref name="r5rs">{{cite journal

|lastlast1=Kelsey |firstfirst1=Richard |last2=Clinger |first2=William |last3=Rees |first3=Jonathan

|date=August 1998

|title=Revised⁵ Report on the Algorithmic Language Scheme

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|doi=10.1023/A:1010051815785

|display-authors=etal}}</ref> and a new standard, ''R6RS'',<ref name="r6rs">{{cite journal

|lastlast1=Sperber |firstfirst1=Michael |last2=Dybvig |first2=R. Kent |last3=Flatt |first3=Matthew |last4=Van Straaten |first4=Anton |last5=Findler |first5=Robby |last6=Matthews |first6=Jacob

|date=August 2009

|title=Revised⁶ Report on the Algorithmic Language Scheme

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|pages=1–301

|doi=10.1017/S0956796809990074

|citeseerx=10.1.1.154.5197 |s2cid=62724224 }}</ref> was ratified in 2007.<ref>{{cite web |url=http://www.r6rs.org/ratification/results.html |title=R6RS ratification-voting results }}</ref> Besides the RnRS standards there are also [[Scheme Requests for Implementation]] documents, that contain additional libraries that may be added by Scheme implementations.

==Timeline==