View source for POP-11

{{External links|date=December 2021}}
{{Use dmy dates|date=April 2022}}
{{Use British English|date=March 2024}}
{{Infobox programming language
| name = POP-11
| logo = <!-- Filename only -->
| logo caption = 
| screenshot = <!-- Filename only -->
| screenshot caption = 
| sampleCode = 
| paradigm = [[Programming paradigm|Multi-paradigm]]: [[Structured programming|structured]], [[Reflective programming|reflective]], [[Procedural programming|procedural]], [[Functional programming|functional]], [[Declarative programming|declarative]]<!-- supports some -->
| family = [[Lisp (programming language)|Lisp]]: POP
| designers = [[Robin Popplestone]], Steve Hardy, Chris Mellish, [[Aaron Sloman]], John Williams, Robert Duncan, Simon Nichols, John Gibson<!-- Best(?) historic order -->
| developers = [[University of Sussex]]<br/>Systems Designers Ltd.<br/>Integral Solutions Ltd.<br/>[[University of Birmingham]]<!-- Historic order -->
| released = {{Start date and age|1975}}
| latest release version = 16
| latest release date = {{Start date and age|2020|01}}
| typing = [[Dynamic typing|dynamic]]
| memory management = 
| scope = 
| programming language = [[POP-11]]
| platform = [[PDP-11]], [[VAX]], [[SPARC]], [[IA-32]], [[PowerPC]], [[x86-64]]<!-- Best historic order -->
| operating system = [[Cross-platform software|Cross-platform]]: [[OpenVMS|VMS]], [[Unix]], [[Linux]], [[macOS|Mac OS X]], [[Windows]]<!-- Best historic order -->
| license = [[Proprietary software|Proprietary]] (1975–1999)<br/>[[Open-source software|Open-source]] (1999–present): [[MIT License|MIT]]–[[XFree86 License|XFree86]]
| file ext = 
| file format = <!-- or: | file formats = -->
| website = {{URL|www.cs.bham.ac.uk/research/projects/poplog/poplog.info.html}}
| implementations = AlphaPop, Basic Pop, Pop-9X, Poplog, Spice
| dialects = 
| influenced by = [[POP-2]]
| influenced = 
}}
'''POP-11''' is a [[Reflective programming|reflective]], [[Dynamic compilation|incrementally compiled]] [[programming language]] with many of the features of an [[interpreted language]]. It is the core language of the [[Poplog]] [[Computer programming|programming]] [[system platform|environment]] developed originally by the [[University of Sussex]], and recently in the School of Computer Science at the [[University of Birmingham]], which hosts the main Poplog website.

POP-11 is an evolution of the language [[POP-2]], developed in [[Edinburgh University]], and features an open [[Stack (data structure)|stack]] model (like [[Forth (programming language)|Forth]], among [[Stack-oriented programming|others]]). It is mainly [[Procedural programming|procedural]], but supports declarative language constructs, including a pattern matcher, and is mostly used for research and teaching in [[artificial intelligence]], although it has features sufficient for many other classes of problems. It is often used to introduce symbolic programming techniques to programmers of more conventional languages like [[Pascal (programming language)|Pascal]], who find POP syntax more familiar than that of [[Lisp (programming language)|Lisp]]. One of POP-11's features is that it supports [[first-class function]]s.

POP-11 is the core language of the Poplog system. The availability of the compiler and compiler subroutines at run-time (a requirement for incremental compiling) gives it the ability to support a far wider range of extensions (including run-time extensions, such as adding new data-types) than would be possible using only a [[Macro (computer science)|macro]] facility. This made it possible for (optional) incremental compilers to be added for [[Prolog]], [[Common Lisp]] and [[Standard ML]], which could be added as required to support either mixed language development or development in the second language without using any POP-11 constructs. This made it possible for Poplog to be used by teachers, researchers, and developers who were interested in only one of the languages. The most successful product developed in POP-11 was the Clementine [[data mining]] system, developed by ISL. After SPSS bought ISL, they renamed Clementine to ''[[SPSS Modeler]]'' and decided to port it to [[C++]] and [[Java (programming language)|Java]], and eventually succeeded with great effort, and perhaps some loss of the flexibility provided by the use of an AI language.

POP-11 was for a time available only as part of an expensive commercial package (Poplog), but since about 1999 it has been freely available as part of the [[open-source software]] version of Poplog, including various added packages and teaching [[Library (computing)|libraries]]. An online version of [[ELIZA]] using POP-11 is available at Birmingham.

At the University of Sussex, David Young used POP-11 in combination with [[C (programming language)|C]] and [[Fortran]] to develop a suite of teaching and interactive development tools for image processing and vision, and has made them available in the Popvision extension to Poplog.

==Simple code examples==
Here is an example of a simple POP-11 program:

 define Double(Source) -> Result;
     Source*2 -> Result;
 enddefine;

 Double(123) =>

That prints out:
 ** 246

This one includes some list processing:

<pre>
<nowiki>
 define RemoveElementsMatching(Element, Source) -> Result;
     lvars Index;
     [[%
     for Index in Source do
         unless Index = Element or Index matches Element then
             Index;
         endunless;
     endfor;
     %]] -> Result;
 enddefine;

 RemoveElementsMatching("the", [[the cat sat on the mat]]) => ;;; outputs [[cat sat on mat]]
 RemoveElementsMatching("the", [[the cat] [sat on] the mat]) => ;;; outputs [[the cat] [sat on] mat]
 RemoveElementsMatching([[= cat]], [[the cat]] is a [[big cat]]) => ;;; outputs [[is a]]
</nowiki>
</pre>

Examples using the POP-11 pattern matcher, which makes it relatively easy for students to learn to develop sophisticated list-processing programs without having to treat patterns as tree structures accessed by 'head' and 'tail' functions (CAR and CDR in Lisp), can be found in the [http://www.cs.bham.ac.uk/research/projects/poplog/doc/popteach/matches online introductory tutorial]. The matcher is at the heart of
[http://www.cs.bham.ac.uk/research/projects/poplog/packages/simagent.html the SimAgent (sim_agent) toolkit]. Some of the powerful features of the toolkit, such as linking pattern variables to inline code variables, would have been very difficult to implement without the incremental compiler facilities.

==See also==
* [[COWSEL]] (aka POP-1) programming language

==References==
{{Reflist}}

* R. Burstall, A. Collins and [[Robin Popplestone|R. Popplestone]], ''Programming in Pop-2'' University Press, Edinburgh, 1968
* D.J.M. Davies, ''POP-10 Users' Manual'', Computer Science Report #25, University of Western Ontario, 1976
* S. Hardy and C. Mellish, 'Integrating Prolog in the Poplog environment', in ''Implementations of Prolog'', Ed., J.A. Campbell, Wiley, New York, 1983, pp 147–162
* R. Barrett, A, Ramsay and A. Sloman, ''POP-11: a Practical Language for Artificial Intelligence'', Ellis Horwood, Chicester, 1985
* M. Burton and N. Shadbolt, ''POP-11 Programming for Artificial Intelligence'', Addison-Wesley, 1987
* J. Laventhol, ''Programming in POP-11'', Blackwell Scientific Publications Ltd., 1987
* R. Barrett and A. Ramsay, ''Artificial Intelligence in Practice:Examples in Pop-11'', Ellis Horwood, Chicester, 1987.
* M. Sharples et al., ''Computers and Thought'', MIT Press, 1987. (An introduction to Cognitive Science using Pop-11. Online version referenced above.)
* James Anderson, Ed., ''Pop-11 Comes of Age: The Advancement of an AI Programming Language'', Ellis Horwood, Chichester, 1989
* G. Gazdar and C. Mellish, ''Natural Language Processing in Pop11/Prolog/Lisp'', Addison Wesley, 1989. ([https://web.archive.org/web/20110709120922/http://www.informatics.sussex.ac.uk/research/groups/nlp/gazdar/nlp-in-pop11/ read online])
* R. Smith, A. Sloman and J. Gibson, POPLOG's two-level virtual machine support for interactive languages, in ''Research Directions in Cognitive Science Volume 5: Artificial Intelligence'', Eds. D. Sleeman and N. Bernsen, Lawrence Erlbaum Associates, pp.&nbsp;203–231, 1992. (Available as Cognitive Science Research Report 153, School of Informatics, University of Sussex).
* Chris Thornton and Benedict du Boulay, ''Artificial Intelligence Through Search'', Kluwer Academic (Paperback version Intellect Books) Dordrecht Netherlands & Norwell, MA USA (Intellect at Oxford) 1992.
* A. Sloman, [http://www.cs.bham.ac.uk/research/projects/poplog/primer Pop-11 Primer], 1999 (Third edition)

==External links==
*{{Official website|www.cs.bham.ac.uk/research/projects/poplog/freepoplog.html}}, Free Poplog Portal
*{{GitHub|GetPoplog}}
* [https://www.cs.bham.ac.uk//research/projects/poplog/examples/ Information about POP-11 teaching materials]
* [http://www.poplog.org The Poplog.org website (including partial mirror of Free poplog web site)] (currently defunct: see [https://web.archive.org/web/20080617130900/http://www.poplog.org/ its more recent copy (Jun 17, 2008)] @ Internet Archive [[Wayback Machine]])
* [http://www.cs.bham.ac.uk/research/projects/poplog/primer/ An Overview of POP-11 (Primer for experienced programmers)] (alt. [http://www.cs.bham.ac.uk/research/projects/poplog/primer.pdf PDF])
* Waldek Hebisch produced a small collection of [http://www.math.uni.wroc.pl/~p-wyk4/pop11_en programming examples] in Pop-11, showing how it can be used for symbol manipulation, numerical calculation, logic and mathematics.
* [http://www.cs.bham.ac.uk/research/projects/poplog/computers-and-thought/ Computers and Thought: A practical Introduction to Artificial Intelligence] '''on-line book''' introducing [[Cognitive science|Cognitive Science]] through Pop-11.
* [http://www.cs.bham.ac.uk/research/projects/poplog/packages/simagent.html The SimAgent (sim_agent) Toolkit]
* [http://www.cs.bham.ac.uk/research/projects/cogaff/eliza/ Pop-11 Eliza] in the [[poplog]] system. [http://www.cs.bham.ac.uk/research/projects/cogaff/eliza/tutorial.txt Tutorial on Eliza]
* [http://www.cs.bham.ac.uk/research/projects/cogaff/poplog-learning-environment.html History of AI teaching in Pop-11] since about 1976.
* [http://www.cs.bham.ac.uk/research/projects/poplog/figs/rclib/ 2-D (X) graphics in Pop-11]
* [http://www.cs.bham.ac.uk/research/projects/poplog/doc/objectclasshelp/objectclass Objectclass] the [[object oriented programming]] extension to Pop-11 (modelled partly on [[CLOS]] and supporting [[multiple inheritance]]).
* [http://www.cs.bham.ac.uk/research/projects/poplog/doc/objectclassteach/objectclass_example Tutorial introduction] to object oriented programming in Pop-11.
* [http://www.cs.bham.ac.uk/research/projects/poplog/doc/pophelp/poprefs Further references]
* [http://www.cs.bham.ac.uk/research/projects/poplog/doc/ Online documentation on Pop-11 and Poplog]
* [http://www.cs.bham.ac.uk/research/projects/poplog/sysdoc/ Online system documentation, including porting information]
* [https://web.archive.org/web/20070910000945/http://hopl.murdoch.edu.au/showlanguage.prx?exp=689&language=Pop-11 Entry for Pop-11 at HOPL (History of Programming Languages) web site]

{{POP programming}}
{{Lisp programming language}}
{{Authority control}}

[[Category:Lisp programming language family]]
[[Category:Artificial intelligence]]
[[Category:History of computing in the United Kingdom]]
[[Category:Science and technology in East Sussex]]
[[Category:University of Sussex]]