NIL (programming language): Difference between revisions

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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 (data structure)|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 [[MacLisp]] 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>