Maclisp

Not to be confused with Macintosh Common Lisp.

Maclisp (or MACLISP, sometimes styled MacLisp or MacLISP) is a programming language, a dialect of the language Lisp. It originated at the Massachusetts Institute of Technology's (MIT) Project MAC^[1] (from which it derived its prefix) in the late 1960s and was based on Lisp 1.5.^[2] Richard Greenblatt was the main developer of the original codebase for the PDP-6;^[1] 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 forks of PDP-6 Lisp, notably BBN Lisp.

Maclisp

Paradigms	Multi-paradigm: functional, procedural, reflective, meta
Family	Lisp
Designed by	Richard Greenblatt Jon L. White
Developer	MIT: Project MAC
First appeared	July 1966; 58 years ago (1966-07)
Typing discipline	dynamic, strong
Implementation language	Assembly language, PL/I
Platform	PDP-6, PDP-10
OS	Incompatible Timesharing System, TOPS-10, TOPS-20, Multics
Filename extensions	.lisp, .fasl
Influenced by
Lisp 1.5
Influenced
Common Lisp, Emacs Lisp

History

Maclisp is a descendant of Lisp 1.5.^[3] Maclisp departs from Lisp 1.5 by using a value cell to access and store the dynamic values of variables;^[4] Lisp 1.5 used a linear search of an association list to determine a variable's value.^[5] 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 (QUOTE A), one could enter 'A to get the same s-expression. Although both implementations put functions on the property list, Maclisp uses different syntax to define functions.^[6] Maclisp also has a load-on-demand feature.^[7]

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?] were added which in other language systems would typically correspond to major release numbers.^{[dubious – discuss]}

Maclisp was used to implement the Macsyma computer algebra system (CAS) or symbolic algebra program. Macsyma's development also drove several features^[which?] 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 and 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 emulators and can be used for experimenting with early AI programs.

Timeline of Lisp dialects

• v
• t
• e

1958	1960	1965	1970	1975	1980	1985	1990	1995	2000	2005	2010	2015	2020
LISP 1, 1.5, LISP 2(abandoned)
		Maclisp
			Interlisp
			MDL
				Lisp Machine Lisp
				Scheme				R5RS		R6RS	R7RS small
				NIL
					ZIL (Zork Implementation Language)
					Franz Lisp
					Common Lisp		ANSI standard
					Le Lisp
					MIT Scheme
					XLISP
						T
						Chez Scheme
						Emacs Lisp
						AutoLISP
						PicoLisp
						Gambit
							EuLisp
							ISLISP
							OpenLisp
							PLT Scheme				Racket
							newLISP
							GNU Guile
									Visual LISP
										Clojure
										Arc
										LFE
											Hy
													Chialisp

Characteristics

Maclisp began with a small, fixed number of data types: cons cell, atom (later termed symbol), integer, and floating-point number. Later additions included: arrays, which were never first-class data types; arbitrary-precision integers (bignums); strings; and tuples. All objects (except inums) were implemented as 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 or compiled. Compiled behavior was the same as interpreted except that local variables were lexical by default in compiled code, unless declared SPECIAL,^[8] 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 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. The various Lisp systems for the Macintosh have no particular similarity to Maclisp.^[9]

References

1. Levy, Steven (1984). Hackers: Heroes of the Computer Revolution. Doubleday. ISBN 0-385-19195-2.
2. Project MAC Progress Report IV: July 1966 to July 1967 (PDF) (Report). n.d. p. 19. Archived from the original (PDF) on March 8, 2016. 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.
3. Moon 1974, p. 1
4. Moon 1974, p. 47
5. Lisp 1.5 p. 13, evaluating an atom e in the environment a is done with (cdr (assoc e a)). That involves a linear search of the association list a. 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.
6. Maclisp uses defun; Lisp 1.5 uses define.
7. Moon 1974, p. 107; the autoload property.
8. Pitman, Kent (December 16, 2007). "The Revised Maclisp Manual (The Pitmanual), Sunday Morning Edition". maclisp.info. HyperMeta, Inc. Declarations and the Compiler, Concept "Variables". Retrieved October 20, 2018. 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.
9. Pitman, Kent (December 16, 2007). "The Revised Maclisp Manual (The Pitmanual), Sunday Morning Edition". maclisp.info. HyperMeta Inc. p. 1 FAQ q1. Retrieved October 20, 2018. Project MAC had nothing to do with the Apple "Mac". And neither did MACLISP.

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. PDF
• McCarthy, John; Abrahams, Paul W.; Edwards, Daniel J.; Hart, Timothy P.; Levin, Michael I. (1985) [1962]. LISP 1.5 Programmer's Manual (2nd ed.). MIT Press. ISBN 0-262-13011-4.
• Moon, David (1974). Maclisp Reference Manual (PDF). Archived (PDF) from the original on 2011-10-05.
• The Revised Maclisp Manual (1983) by Kent Pitman
• The Multics MACLISP compiler (1977) by Bernard Greenberg