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{{Infobox programming language
| name = MultiLisp
| logo = <!-- Filename only -->
| logo caption = 
| screenshot = <!-- Filename only -->
| screenshot caption = 
| paradigms = Multi-paradigm: [[Functional programming|functional]], [[Imperative programming|imperative]], [[Concurrent computing|concurrent]], [[Metaprogramming|meta]]
| family = [[Lisp (programming language)|Lisp]]
| designer = Robert H. Halstead Jr.
| developer = [[Organization:Massachusetts Institute of Technology|Massachusetts Institute of Technology]] (MIT
| released = {{Start date and age|1980}}<!--Add |mm|dd| if known-->
| latest release version = 
| latest release date = <!-- {{Start date and age|1985|MM|DD|df=yes}} -->
| typing = Dynamic, [[Latent typing|latent]], strong
| scope = [[Scope (computer science)#Lexical scoping and dynamic scoping|Lexical]]
| programming language = [[Interlisp]]
| discontinued = Yes
| platform = Concert [[Multiprocessing|multiprocessor]]
| operating system = 
| license = [[Proprietary software|Proprietary]]
| file ext = 
| file format = <!-- or: | file formats = -->
| website = <!-- {{URL|www.example.com}} -->
| implementations = 
| dialects = 
| influenced by = [[Lisp (programming language)|Lisp]], [[Scheme (programming language)|Scheme]]
| influenced = [[Gambit (Scheme implementation)|Gambit]], [[Interlisp]]-[[VAX]]
}}
'''MultiLisp''' is a [[Functional programming|functional]] [[Programming language|programming language]], a [[Dialect (computing)|dialect]] of the language [[Lisp (programming language)|Lisp]], and of its dialect [[Scheme (programming language)|Scheme]], extended with constructs for [[Parallel computing|parallel computing]] execution and [[Shared memory|shared memory]]. These extensions involve [[Side effect (computer science)|side effects]], rendering MultiLisp [[Nondeterministic programming|nondeterministic]]. Along with its parallel-programming extensions, MultiLisp also had some unusual [[Garbage collection (computer science)|garbage collection]] and task scheduling algorithms. Like Scheme, MultiLisp was optimized for [[Computer algebra|symbolic computing]]. Unlike some parallel programming languages, MultiLisp incorporated constructs for causing side effects and for explicitly introducing parallelism.

It was designed by Robert H. Halstead Jr., in the early 1980s for use on the 32-processor Concert [[Multiprocessing|multiprocessor]] then being developed at [[Organization:Massachusetts Institute of Technology|Massachusetts Institute of Technology]] (MIT) and implemented in [[Interlisp]]. It influenced the development of the Scheme dialects [[Gambit (Scheme implementation)|Gambit]],<ref>{{cite web |url=http://dynamo.iro.umontreal.ca/wiki/index.php/Main_Page  |title=Gambit |author=WikiSysop |author2=Mikaelm |author3=Bjlucier |last4=Thedens |first4=Dan |date=2019-02-06 |access-date=2019-04-21}}</ref> and Interlisp-[[VAX]].

==PCALL and FUTURE==
MultiLisp achieves parallelism with the PCALL [[Macro (computer science)|macro]], where

<code>(PCALL Fun A B C ...)</code>

is equivalent to

<code>(Fun A B C ...)</code>

except that the [[Parameter (computer programming)|argument]]s <code>A, B, C,</code> etc. are explicitly allowed to be evaluated in parallel; this circumvents the usual order of evaluation, which is sequential and left to right. It also makes use of a parallel programming construct called futures, which resembles [[Fork (system call)|forking]], combined with [[Lazy evaluation|lazy evaluation]]. Using this construct, an expression such as

<code>([[Cons|cons]] (FUTURE A) (FUTURE B))</code>

can be written, which will overlap the evaluation of the expressions A and B, not only with each other, but with computations that use the result of the [[Cons|cons]] call, until an operation is performed that needs correct information about the value of A or B.

==See also==
*Speculative evaluation

==References==
{{Reflist}}
*{{cite journal |last=Halstead |first=Robert H. Jr. |date=October 1985 |title=MultiLisp: A Language for Concurrent Symbolic Computation |journal=[[ACM Transactions on Programming Languages and Systems]] |volume=7 |issue=4 |pages=501–538 |doi=10.1145/4472.4478 |s2cid=1285424 |doi-access=free }}
*{{cite thesis |last=Koomen |first=Johannes A. G. M. |date=1980 |title=The Interlisp Virtual Machine: A Study of its Design and its Implementation as Multilisp |type=MSc |publisher=University of British Columbia }}
*{{cite conference |title=Implementation of Interlisp on the VAX |last1=Bates |first1=Raymond L. |last2=Dyer |first2=David |last3=Koomen |first3=Johannes A. G. M. |date=15–18 August 1982 |book-title=LFP '82 Proceedings of the 1982 ACM symposium on LISP and functional programming |pages=81–87 |location=Pittsburgh, Pennsylvania, United States |conference=ACM symposium on LISP and functional programming }}
*{{cite conference |title=The MultiLisp Language: Lisp for a Multiprocessor |last=Halstead |first=Robert H. Jr. |date=1984 |location=Tokyo, Japan |conference=Conference on 5th Generation Computers }}
*{{cite journal |last=Martins |first=W.S. |title=Parallel Implementations of Functional Languages |journal=Proceedings of the 4th Int. Workshop on the Parallel Implementation of Functional Languages |pages=92 }}
*{{cite journal |last1=Skillicorn |first1=David B. |last2=Talia |first2=Domenico |date=June 1998 |title=Models and languages for parallel computation |journal=[[ACM Computing Surveys]] |volume=30 |issue=2 |pages=123–169 |doi=10.1145/280277.280278 |s2cid=9308854 |doi-access=free }}

{{Lisp programming language}}

[[Category:Concurrent programming languages]]
[[Category:Dynamically typed programming languages]]
[[Category:Functional languages]]
[[Category:Lisp programming language family]]
[[Category:Multi-paradigm programming languages]]

{{Sourceattribution|MultiLisp}}