Designed by Jon L White Typing discipline dynamic, strong | First appeared 1970s | |
Paradigm multi-paradigm: functional, procedural Developer Jon L White, Guy L. Steele, Jr. and Richard P. Gabriel | ||
NIL is a 32-bit implementation of Lisp developed at MIT and intended to be the successor to Maclisp. NIL stands for "New Implementation of LISP", and was in part a response to DECs VAX computer. The project was headed by Jon L White, with a stated goal of maintaining compatibility with MacLisp whilst fixing many of the problems with the language.
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History
The Lisp language was invented in 1958 by John McCarthy while he was at MIT. From its inception, Lisp was closely connected with the artificial intelligence research community, especially on PDP-10 systems. Lisp was used as the implementation of the programming language Micro Planner that was the foundation for the famous AI system SHRDLU. Lisp, in particular 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 (Lisp would use stop-and-copy garbage collection of its single heap for memory allocation) 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 machines: 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 DEC VAX.
NIL was an implementation of 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, as opposed to Lisp Machine Lisp for the Lisp machines. "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 ) 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 bignums was a requirement to support Macsyma, since NIL would be a failure with slow bignums. 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.
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 Lisp; and secondly, Jonathan Rees worked on part of the NIL project during a year away from 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 system known as T. In part NIL begat this name, since "T is not NIL".