View source for Maclisp

{{Short description|Dialect of Lisp programming language}}
{{distinguish|Macintosh Common Lisp}}
{{Infobox programming language
| name = Maclisp
| logo = <!-- (filename) -->
| logo caption = 
| screenshot = <!-- (filename) -->
| screenshot caption = 
| paradigms = [[Multi-paradigm programming language|Multi-paradigm]]: [[Functional programming|functional]], [[Procedural programming|procedural]], [[Reflection (computer programming)|reflective]], [[Metaprogramming|meta]]
| family = [[Lisp (programming language)|Lisp]]
| designer = [[Richard Greenblatt (programmer)|Richard Greenblatt]]<br />Jon L. White
| developer = [[Massachusetts Institute of Technology|MIT]]: [[Project MAC]]
| released = {{Start date and age|1966|07}}
| latest release version = 
| latest release date = <!-- {{Start date and age|1985?|MM|DD|df=yes}} -->
| typing = [[Dynamic typing|dynamic]], [[Strong and weak typing|strong]]
| scope = 
| programming language = [[Assembly language]], [[PL/I]]
| discontinued = Yes
| platform = [[PDP-6]], [[PDP-10]]
| operating system = [[Incompatible Timesharing System]], [[TOPS-10]], [[TOPS-20]], [[Multics]]
| license = 
| file ext = {{Mono|.lisp}}, {{Mono|.fasl}}
| file format = <!-- or: | file formats = -->
| website = <!-- {{URL|www.example.com}} -->
| implementations = 
| dialects = 
| influenced by = Lisp 1.5
| influenced = [[Common Lisp]], [[Emacs Lisp]]
}}
'''Maclisp''' (or '''MACLISP''', sometimes styled '''MacLisp''' or '''MacLISP''') is a [[programming language]], a [[Dialect (computing)|dialect]] of the language [[Lisp (programming language)|Lisp]]. It originated at the [[Massachusetts Institute of Technology]]'s (MIT) [[Project MAC]]<ref name="hackers">{{cite book |last=Levy |first=Steven |author-link=Steven Levy |title=[[Hackers: Heroes of the Computer Revolution]] |publisher=Doubleday |year=1984 |isbn=0-385-19195-2}}</ref> (from which it derived its prefix) in the late 1960s and was based on Lisp 1.5.<ref>{{cite report |title=Project MAC Progress Report IV: July 1966 to July 1967 |date=n.d. |page=19 |quote=The higher-level language used for most of the vision laboratory program is the PDP-6 LISP System. This system is based chiefly on the LISP 1.5 programming language, but has been extensively modified in a number of ways. These include many new functions and services, including facilities for linking with programs written in other languages. |url=http://www.dtic.mil/dtic/tr/fulltext/u2/681342.pdf |url-status=dead |archive-url=https://web.archive.org/web/20160308100743/http://www.dtic.mil/dtic/tr/fulltext/u2/681342.pdf |archive-date=March 8, 2016}}</ref> [[Richard Greenblatt (programmer)|Richard Greenblatt]] was the main developer of the original codebase for the [[PDP-6]];<ref name="hackers" /> Jon L. White was responsible for its later maintenance and development.  The name ''Maclisp'' began being used in the early 1970s to distinguish it from other [[Fork (software development)|fork]]s of PDP-6 Lisp, notably [[BBN Lisp]].

==History==
Maclisp is a descendant of [[Lisp 1.5]].<ref>{{harvnb|Moon|1974|p=1}}</ref>  Maclisp departs from Lisp 1.5 by using a ''value cell'' to access and store the dynamic values of [[Variable (computer science)|variables]];<ref>{{harvnb|Moon|1974|p=47}}</ref> Lisp 1.5 used a linear search of an association list to determine a variable's value.<ref>Lisp 1.5 p. 13, evaluating an atom <code>e</code> in the environment <code>a</code> is done with <code>(cdr (assoc e a))</code>.  That involves a linear search of the association list <code>a</code>. A more involved description with global constants and errors is given on p. 71; it does a linear search of the property list before searching the association list.</ref>  The Maclisp variable evaluation is faster but has different variable semantics.  Maclisp also employed reader macros to make more readable ''input'' and ''output'', termed [[input/output]] (I/O).  Instead of entering <code>(QUOTE A)</code>, one could enter <code>'A</code> to get the same [[s-expression]]. Although both implementations put functions on the property list, Maclisp uses different syntax to define functions.<ref>Maclisp uses <code>defun</code>; Lisp 1.5 uses <code>define</code>.</ref>  Maclisp also has a load-on-demand feature.<ref>{{harvnb|Moon|1974|p=107}}; the <code>autoload</code> property.</ref>

Maclisp began on [[Digital Equipment Corporation]] [[PDP-6]] and [[PDP-10]] computers running the [[Incompatible Timesharing System]] (ITS); later it was ported to all other PDP-10 operating systems, for example, ''Timesharing / Total Operating System'', [[TOPS-10]] and [[TOPS-20]].  The original implementation was in [[assembly language]], but a later implementation on [[Multics]] used [[PL/I]].  Maclisp developed considerably in its lifetime.  Major features{{which|date=March 2016}} were added which in other language systems would typically correspond to major release numbers.{{dubious|date=March 2016}}<!-- distinguish the langage and the library; LET, SETF, and LOOP, for example, did not change the language. Compare with UNWIND-PROTECT. -->

Maclisp was used to implement the [[Macsyma]] [[computer algebra system]] (CAS) or symbolic algebra program. Macsyma's development also drove several features{{which|date=March 2016}}<!-- BIGNUM and what else? --> in Maclisp. The [[SHRDLU]] blocks-world program was written in Maclisp, and so the language was in widespread use in the [[artificial intelligence]] (AI) research community through the early 1980s.  It was also used to implement other programming languages, such as [[Planner (programming language)|Planner]] and [[Scheme (programming language)|Scheme]].  Multics Maclisp was used to implement the first Lisp-based [[Emacs]].

Maclisp was an influential Lisp implementation, but is no longer maintained actively. It now runs on PDP-10 [[emulator]]s and can be used for experimenting with early AI programs.

{{Lisp}}

==Characteristics==
Maclisp began with a small, fixed number of [[data type]]s: [[cons]] cell, atom (later termed ''symbol''), [[integer]], and [[Floating-point arithmetic|floating-point number]].  Later additions included: [[Array data type|arrays]], which were never first-class data types; [[Arbitrary-precision arithmetic|arbitrary-precision integers]] (bignums); [[String (computer science)|strings]]; and [[tuple]]s.  All objects (except inums) were implemented as [[Pointer (computer programming)|pointers]], and their data type was determined by the block of memory into which it pointed, with a special case for small numbers (inums).

Programs could be ''[[Interpreted language|interpreted]]'' or ''[[Compiler|compiled]]''.  Compiled behavior was the same as interpreted except that local variables were lexical by default in compiled code, unless declared SPECIAL,<ref>{{cite web |url=http://maclisp.info/pitmanual/complr.html#23.1.2 |title=The Revised Maclisp Manual (The Pitmanual), Sunday Morning Edition |last=Pitman |first=Kent |date=December 16, 2007 |website=maclisp.info |publisher=HyperMeta, Inc. |access-date=October 20, 2018 |at=Declarations and the Compiler, Concept "Variables" |quote= If the variable to be bound has been declared to be special, the binding is compiled as code to imitate the way the interpreter binds variables.}}</ref> and no error checking was done for inline operations such as CAR and CDR.  The Ncomplr compiler (mid-1970s) introduced fast numeric support to Lisp languages, generating [[machine code]] (instructions) for arithmetic rather than calling interpretive routines which dispatched on data type.  This made Lisp arithmetic comparable in speed to [[Fortran]] for scalar operations (though Fortran array and loop implementation remained much faster).

The original version was limited by the 18-bit word [[memory address]] of the PDP-10, and considerable effort was expended in keeping the implementation lean and simple. Multics Maclisp had a far larger address space, but was costly to use.  When the memory and processing power of the [[PDP-10]] were exceeded, the [[Lisp Machine]] was invented: [[Lisp Machine Lisp]] is the direct descendant of Maclisp.  Several other [[Lisp (programming language)|Lisp]] dialects were also in use, and the need to unify the community resulted in the modern [[Common Lisp]] language.

==Name==
Maclisp was named for [[Project MAC]], and is unrelated to Apple's [[Macintosh]] (Mac) computer, which it predates by decades or to [[John McCarthy (computer scientist)|John McCarthy]]. The various Lisp systems for the Macintosh have no particular similarity to Maclisp.<ref>{{cite web |url=http://maclisp.info/pitmanual/ |title=The Revised Maclisp Manual (The Pitmanual), Sunday Morning Edition |last=Pitman |first=Kent |date=December 16, 2007 |website=maclisp.info |publisher=HyperMeta Inc. |access-date=October 20, 2018 |at=p. 1 FAQ q1 |quote=Project MAC had nothing to do with the Apple "Mac". And neither did MACLISP.}}</ref>

==References==
{{Reflist}}

==External links==
* http://www.softwarepreservation.org/projects/LISP/maclisp_family/ contains a bibliography of Maclisp.
** John L. White. An Interim LISP User's Guide. Artificial Intelligence Memo No. 190, Project MAC, Massachusetts Institute of Technology, March 1970, 87 pages. ftp://publications.ai.mit.edu/ai-publications/pdf/AIM-190.pdf states "'MACLISP' refers to the PDP/6 implementation of the programming language LISP in use at the Artificial Intelligence Group of Project MAC."
** "In 1973 and 1974, [[David A. Moon]] led an effort to implement MacLisp on the Honeywell 6180 under Multics. As a part of this project he wrote the first truly comprehensive reference manual for Maclisp, which became familiarly known as the 'Moonual'." [Steele and Gabriel 1993]
** Jon L. White [JONL], Eric Rosen [ECR], [[Richard M. Stallman]] [RMS], [[Guy L. Steele Jr.]] [GLS], Howard I. Cannon [HIC], Bob Kerns [RWK]. LISP News. MacLisp release notes.
** Jon L. White. LISP: Program is Data: A Historical Perspective on MacLISP. Proceedings of the 1977 MACSYMA Users' Conference. NASA Scientific and Technical Information Office (Washington, D.C., July 1977), pages 181–189. [http://www.softwarepreservation.org/projects/LISP/MIT/White-Program_Is_Data-1977-From_MACSYMA77.pdf PDF]
* {{Cite book |first1=John |last1=McCarthy |author1-link=John McCarthy (computer scientist) |first2=Paul W. |last2=Abrahams |first3=Daniel J. |last3=Edwards |first4=Timothy P. |last4=Hart |first5=Michael I. |last5=Levin |title=LISP 1.5 Programmer's Manual |publisher=[[MIT Press]] |isbn=0-262-13011-4 |orig-year=1962 |edition=2nd |year=1985 |url=https://archive.org/details/lisp15programmer00john |url-access=registration }}
* {{cite book |last=Moon |first=David |author-link=David A. Moon |title=Maclisp Reference Manual |date=1974 |url=http://www.softwarepreservation.org/projects/LISP/MIT/Moon-MACLISP_Reference_Manual-Apr_08_1974.pdf |archive-url=https://web.archive.org/web/20111005010120/http://www.softwarepreservation.org/projects/LISP/MIT/Moon-MACLISP_Reference_Manual-Apr_08_1974.pdf |archive-date=2011-10-05 |url-status=live }}
* [http://maclisp.info/pitmanual/ ''The Revised Maclisp Manual''] (1983) by [[Kent Pitman]]
* [http://www.multicians.org/lcp.html ''The Multics MACLISP compiler''] (1977) by [[Bernard Greenberg]]

{{Lisp programming language}}
{{Multics}}

[[Category:Lisp programming language family]]
[[Category:Lisp (programming language)]]
[[Category:Multics software]]