NIL (programming language): Difference between revisions

Revision as of 16:28, 15 March 2010

Revision as of 08:18, 8 September 2010

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| url = http://www.dreamsongs.com/NewFiles/Timrep.pdf

| date = May 1985

| isbn = 978-0-262-07093-5; LCCN: 85-15161}} <!-- xiv, 285 p. ; 23 cm. Cambridge, Mass. --></ref> implementation of [[Lisp (programming language)|Lisp]] developed at [[Massachusetts Institute of Technology|MIT]] and intended to be the successor to [[Maclisp|MacLisp]].<ref name=STEELE>{{cite web | title=The evolution of Lisp| author=Guy L Steele Jr, Richard P Gabriel | url=http://www.dreamsongs.com/NewFiles/HOPL2-Uncut.pdf | accessdate=2006-10-12}}</ref> NIL stood for "New Implementation of LISP", and was in part a response to [[Digital Equipment Corporation|DECs]] [[VAX]] computer. The project was headed by [[Jon L White]] <ref>{{cite web | title=Brief History of the Lisp Language| author=Kent M Pitman | url=http://www.lisp.org/table/Lisp-History.html | accessdate=2006-10-12}}</ref>, with a stated goal of maintaining compatibility with MacLisp whilst fixing many of the problems with the language.

==History==

The [[Lisp (programming language)|Lisp]] language was invented in 1958 by [[John McCarthy (computer scientist)|John McCarthy]] while he was at [[Massachusetts Institute of Technology|MIT]]<ref>{{cite web|title=History of LISP|author=Paul McJones|url=http://community.computerhistory.org/scc/projects/LISP/|accessdate=2006-10-12}}</ref>. From its inception, Lisp was closely connected with the [[artificial intelligence]] research community, especially on [[PDP-10]]<ref>The 36-bit word size of the [[PDP-6]]/[[PDP-10]] was influenced by the usefulness of having two Lisp 18-bit pointers in a single word. "The PDP-6 project started in early 1963, as a 24-bit machine. It grew to 36 bits for LISP, a design goal." [http://groups.google.com/group/alt.folklore.computers/browse_thread/thread/6e5602ce733d0ec/17597705ae289112]</ref> systems. Lisp was used as the implementation of the programming language [[Planner programming language|Micro Planner]] that was the foundation for the famous AI system [[SHRDLU]]. Lisp, in particular [[Maclisp|MacLisp]] (so called because it originated at MIT's project MAC) was also used to implement the [[Macsyma]] [[computer algebra system]]. In the 1970s, as AI research spawned commercial offshoots, the performance of existing Lisp systems became a growing issue.

Partly because of [[garbage collection (computer science)|garbage collection]] (NIL would use stop-and-copy garbage collection of its single heap for [[Dynamic memory allocation|memory allocation]]<ref name="GABRIEL"/>) and partly because of its representation of internal structures, Lisp became difficult to run on the memory-limited stock hardware of the day. This led to the creation of [[LISP machine]]s: dedicated hardware for running Lisp environments and programs. An alternative was to use the more powerful commodity hardware which was becoming available, in particular the [[Digital Equipment Corporation|DEC]] [[VAX]].

NIl was an implementation of [[Lisp (programming language)|Lisp]] developed at [[MIT]] in the mid to late 1970s, and intended to be a modern successor to [[MacLispMaclisp]] that was suitable for running on stock hardware<ref name=STEELE/>, as opposed to [[Lisp Machine Lisp]] for the Lisp machines.<ref name="GABRIEL"/> "Originally designed as the first modern Lisp dialect on stock hardware after the development of Lisp- machine Lisp at MIT, it went on to become one of the main influences on the design of Common Lisp." (pg 63/294 of <ref name=GABRIEL/>) Since the users of the [[Macsyma]] program represented a large potential user base for NIL, it was necessary that NIL would be a large, complex system, and that speed would be imperative. For example high-speed [[bignum]]s was a requirement to support Macsyma, since NIL would be a failure with slow bignums.<ref>{{cite web | title=Dan Weinreb on NIL| url=http://www.paulgraham.com/weinreb.html|accessdate=2006-10-12}}</ref> Consequently NIL ended up with a large base of VAX assembly language. These requirements led to a very aggressive and complex optimization strategy which was applied prematurely, with negative results on the final system.<ref name=SHIVERS>{{cite web | title=History of T | author=Olin Shivers | url=http://www.paulgraham.com/thist.html | accessdate=2006-10-12}}</ref>

Concurrently with the effort to write NIL, a research group at [[Stanford University]] and

[[Lawrence Livermore National Laboratory]] headed by [[Richard P. Gabriel]] were investigating the design of a Lisp to run on the S-1 Mark IIA supercomputer, [[S-1 Lisp]]. S-1 Lisp was never fully functional, but was a test bed for implementing advanced compiler techniques in a Lisp. Eventually the S-1 and NIL groups began to collaborate.

Although not successful as a project, NIL was important in a number of ways: firstly it brought together [[Jon L. White]], [[Guy L. Steele, Jr.]] and Richard P. Gabriel, who were to later to go and define [[Common LISPLisp]] <ref name=STEELE/>; and secondly, Jonathan Rees worked on part of the NIL project during a year away from [[Yale University|Yale]]. On returning to Yale, he was hired by the computer science department to write a new Lisp, which became the optimizing, native code [[Scheme (programming language)|Scheme]] system known as [[T (programming language)|T]]. In part NIL begat this name, since "T is not NIL".<ref name=SHIVERS/>

==Quotes about NIL==