General Information: This article contains the answers to some Frequently Asked Questions (FAQ) often seen in news://comp.lang.prolog/. It is posted (twice a month, currently on the 2nd and 16th) to help reduce volume in this newsgroup and to provide hard-to-find information of general interest.
The World Wide Web URL for this FAQ is: http://www.logic.at/prolog/faq/
Please send questions about the FAQ and updates to
1. What is the Association for Logic Programming?
To keep up with the current state of logic programming technology, readers can join the Association for Logic Programming (ALP) and receive their Newsletter. For details on how to join or send in contributions, check http://www.cs.nmsu.edu/ALP/ or contact
The Prolog Resource Guide (v0.6) was printed in issue 5/1 of the Newsletter (Feb. 1992). This lists information concerning Prolog Archives, Books, Suppliers, etc. It is now maintained by Mark Kantrowitz (
<Mark.Kantrowitz@glinda.oz.cs.cmu.edu>), and used to be posted periodically to news://comp.lang.prolog.
2. Where can I get a free Prolog for system X (PC, Mac, Unix or other)?
The following are anonymous-FTP sites for free Prologs (or related languages) which are either in the public domain or are "copy-lefted" (permitted to be copied with some restrictions on commercial use).
(Please note that for extensive development work, users will probably want a robust interpreter or compiler with good debugging facilities and a standard syntax, among other things. While public-domain systems are a valuable service to the community, they do not necessarily have all these things, and users should weigh carefully what they want to do against the capabilities and costs of the available systems.)
E-mail: Rudolf Opalla
Info: WAM-based language with narrowing/rewriting
Platforms: Window, Linux and Solaris
Info: Registration is compulsory, except for the Free Academic/Personal/Evaluation License.
Info: High performance, commercial functionality except debugging and modules.
Platforms: Solaris 1.x and HP-UX 9.x
Contact: Takao Doi
Info: Arity/Prolog32 provides a complete Prolog programming environment in which you can write, debug, and run Prolog programs in 32-bit Windows environments (95/98/NT/2000). Arity/Prolog32 is a powerful, highly optimized, and extended version of the logic programming language Prolog. Arity/Prolog32 is a complete compiler and interpreter written in Prolog, C, and Assembly language and is a superset of Clocksin and Mellish Prolog.
Platforms: Win32, Solaris, SunOS, UNIX, FreeBSD and Linux
E-mail: Neng-Fa Zhou
Info: Free of charge for individual users.
Platforms: Windows 95/98/NT, Linux and all major Unix platforms.
Info: Download free evaluation copies and see online demos. Inexpensive Educational licensing available.Has built-in networking, multi-threading, mobile code and distributed blackboards. Supports BinNet Internet Programming Tool kit.
Platforms: Transputer systems
Info: BAP is a parallel prolog system for Transputer systems. Available under a Berkely style of copyright.
Platforms: Win32, UNIX
E-mail: John Pool
Info: A Prolog interpreter written in C#. Can easily be integrated in C# programs. Characteristics: reliable and quite fast beta version, command line interface, builtin DCG, XML-predicates, persistent predicates (using Firebird RDBMS), extendible.
Platforms: Linux, Win32 (95/98/NT), Solaris, SunOS, UNIX in general.
Info: Next generation LP/CLP system. Commercial functionality, but freely available w/source. ISO-Prolog + modules, networking, multi-threading, clp(r), clp(q), interfaces (Java, C, tcltk, WWW, databases/ODBC, ...), functions, higher-order, records, persistence, objects, assertions (types, modes, ...), source debugger, auto-documenter, static debugger, and more.
Contact: Daniel Diaz
Info: Constraint logic programming over finite domains. Requires GNU C v.2.4.5 or higher.
Contact: Yan Georget
Info: Requires GNU C (gcc) version 2.4.5. or higher.
Available: E-mail request from Joxan Jaffar
Info: Constraint logic programming language, for academic and research purposes only.
Platforms: UNIX, MacOS X, Windows
Info: Open source (GPL) implementation supporting Unicode, threads, sockets, processes, contexts, imperative data structures, and interfaces with C/C++, Java, and wxWidgets
Contact: Artur Miguel Dias
Platforms: Solaris, Linux, Linux/Alpha, Mac OS X, Windows
Info: ECLiPSe is a Prolog and Constraint Programming platform with a long history and has been open-source since Sept 2006.
Platforms: Windows 95/98/NT/2000/XP, Linux, Solaris, AIX, HP-UX and other UNIX platforms
Info: IF Prolog is a commercial Prolog system with interfaces to C/C++, Java, sockets, Windows events and a COM servers. A graphical debugger allows step-forward, step backward debugging of Prolog code. A static module concept allows many additional errors to be detected at compile time. Constraint Programming (for finite domains, intervals and booleans using global constraints and linear optimisation).
License: Free evaluation copies and inexpensive educational licensing available.
Platforms: Many Unixes, Windows, MacOS X
E-mail: Daniel Diaz
Info: Multi-threaded, Java based Prolog interpreter with built-in networking, distributed blackboards and mobile code (inexpensive shareware licensing available).
Info: Java Internet Prolog is a cross-platform pure Java 100% prolog interpreter that supplies Java world with the power of prolog language and provides prolog language with a technology to implement new predicates in Java.
Info: ICOT Free Software. Concurrent logic programming. Tested on Sparcs, DEC 7000, Gateway P5-60.
Available: Available from http://www.lpa.co.uk/ind_dow.htm
Info: Proprietary commercial ISO-Prolog Compiler in 100% Java support for web programming, XML, servlets, applets, standalones. Free evaluation license.
Platforms: SPARC, DECstation, MIPS, HP 9000 series, Sun 3.
Platforms: Apple Macintosh
<email@example.com>. (Michael Brady).
Platforms: Various Unixes, including Sun, Dec Alpha, HP and many others. Also a Win32 version is available. Sources available for other combinations.
Available: At the Free Poplog Web/FTP site, including full sources http://www.cs.bham.ac.uk/research/poplog/freepoplog.html
Info: Robust incremental compiler, part of the multi-language Poplog system (including Common Lisp, Pop-11 and Standard ML). Unix, Linux & VMS versions include full support for X window facilities/Motif. More information at http://www.cs.bham.ac.uk/research/poplog/poplog.info.html Licence modelled on XFree86. Can be freely distributed, though copyright is owned by Sussex University and ISL.
Available: On CompuServe in the AIEXPERT forum, interpreter and examples in PIE2.ZIP, documentation in PIEDOC.ZIP.
E-mail: Brent Ruggles
Platforms: UNIX, Linux, beta for MAC
Info: Extended WAM with support for quantifiers and substitutions, multi-threaded, high-level communication.
Platforms: Unix, Linux, Windows and Mac
Info: A modern Prolog system written mostly in Rust.
Platforms: Windows 95/NT, plans for UNIX and Macintosh
Platforms: Binaries for Linux, Windows (NT/2000/XP/Vista) and Mac OS X (darwin). Sources: ANSI-C, both 32 and 64-bit machines, compiles on almost all Unix systems and more.
Info: Complete, ISO and Edinburgh standard, common optimizations, GC including atoms. Portable graphics, multiple threads, constraints, comprehensive libraries for (semantic) web programming, Unicode, source-level debugger, advanced syntax colouring
License: Simplified BSD. Run license/0 for more information.
Platforms: Windows 95/98/NT 4.0, plans for Windows 2000, Linux and Sun Solaris
Info: Includes all the facilities necessary to write mission critical commercial-grade applications. Fully visual development environment. Open architecture. Object-oriented. Built-in database system and ODBC support. Visual Prolog Personal Edition is available on a freeware license.
Info: Compiler which translates Prolog to C via WAM. Debuggers. Requires GNU C v.2.4.5 or higher.
Contact: Daniel Diaz
Platforms: Apple Macintosh OS X, 10.2.3+
Info: XGP is an open source (GPL) integrated development environment with user interface and graphics support based on gprolog and Cocoa under Macintosh OS X.
Platforms: Many, including SunOS, Linux and Windows
Info: system with SLG-resolution, HiLog syntax, and unification factoring.
Platforms: UNIX-based platforms and Windows
E-mail: Vitor Santos Costa
Info: Yap is entirely written in C and Prolog and should be portable to most 32-bit and 64-bit Unix based platforms. A Windows port is also available. Yap4.2 is distributed under Perl's artistic license and can be freely distributed.
3. What commercial systems are available? What about systems available for a price from research institutions?
Many commercial systems are listed in the Prolog Resource Guide. The Resource Guide also lists many systems which are not exactly "commercial", but available for a price from research institutions. The list of such systems was originally compiled by Chris Moss, of Imperial College. The rest of the Resource Guide was originally compiled by Dag Wahlberg, of Uppsala University.
The Prolog Resource Guide hasn't been updated lately, but nevertheless still contains some valuable information. It can be found at http://www-2.cs.cmu.edu/Groups/AI/html/faqs/lang/prolog/prg/top.html.
4. How do I get in touch with my Prolog's users' group, sales representative, or technical support line?
Here are some e-mail addresses of these contacts, listed alphabetically by company or major product name.
Web site: http://alsprolog.com
Web site: http://www.amzi.com
Web site: http://www.clip.dia.fi.upm.es/Software
Web site: http://www.cosytec.com
<firstname.lastname@example.org> (or .fr)
<email@example.com> (or .fr)
Web site: http://eclipseclp.org
Web site: http://www.gprolog.org/
Formerly BIM ProLog
PDC Prolog is the succesor to Turbo Prolog and the predecessor to Visual Prolog.
Web site: http://quintus.sics.se
Mailing list: see http://www.sics.se/isl/quintuswww/site/community.html
Web page: http://www.sics.se/sicstus
Mailing list: see http://www.sics.se/isl/sicstuswww/site/community.html
Turbo Prolog is the predecessor of PDC Prolog (see above).
5. I think language X is better than Prolog. What do you think?
These debates rarely result in any productive discussion. To some extent, one's favourite language is based on irrational ideology.
However, many people now agree that different languages are good for different things. Prolog seems to be good for problems in which logic is intimately involved, or whose solutions have a succinct logical characterization. Like other interactive, symbolic languages, Prolog is also good for rapid prototyping.
Also, note that there are many different "Prologs" and other logic programming languages available, all with different capabilities.
6. What are the recent developments?
There are some languages in development which do not have Prolog syntax, but do subsume and generalize Prolog's logic programming abilities.
Some other languages bring new developments while also supporting Prolog syntax and functionality as an option:
Web site: http://www.clip.dia.fi.upm.es/Software
7. My Prolog prof assigned me this problem. Can you help me with it?
If your instructor assigned it to you, he or she probably wanted you to do it yourself. If it's an introductory Prolog course, your question might be elementary to most readers, so it might be a waste of network resources to ask it. Please ask your instructor, a friend, a teaching assistant, or a local newsgroup for help first.
That being said, there are news://comp.lang.prolog/ readers who would be glad to help people making a legitimate attempt to learn Prolog.
8. Can you suggest some books on Prolog?
The Prolog Resource Guide (see above) contains a listing of Prolog books. It is maintained by Mark Kantrowitz (
<Mark.Kantrowitz@glinda.oz.cs.cmu.edu>), and posted periodically on news://comp.lang.prolog.
Here are some of the most popular books on Prolog.
"Programming In Prolog". William F. Clocksin and Christopher S. Mellish. Springer-Verlag, 2003 (5th ed).
"Prolog for Programmers". Feliks Kluzniak and Stanislaw Szpakowicz. Academic Press, London, 1985, now available without charge from https://sites.google.com/site/prologforprogrammers/
"Prolog Programming for Artificial Intelligence". Ivan Bratko. Addison-Wesley, 2001 (3rd ed).
"The Art of Prolog: Advanced Programming Techniques". Leon Sterling and Ehud Shapiro. MIT Press, 1994 (2nd ed).
"The Craft of Prolog". Richard A. O'Keefe. MIT Press, 1990.
"Foundations of Logic Programming". John Lloyd. Springer-Verlag, 1988 (2nd ed).
"Logic, Programming and Prolog". Ulf Nilsson and Jan Maluszynski. Originally published by John Wiley & Sons Ltd (2nd ed. 1995) and now available without charge from http://www.ida.liu.se/~ulfni/lpp
"Building Expert Systems in Prolog". Dennis Merritt. Springer-Verlag, 1989. HTML & PDF versions available from http://www.amzi.com/ExpertSystemsInProlog
9. Are there any WWW archives of comp.lang.prolog ?
Yes, there are: Google Groups has archives of news://comp.lang.prolog/. They can be found at https://groups.google.com/forum/#!forum/comp.lang.prolog
10. How can I get the ISO Prolog standard? Where can I go for more information about it?
You can obtain the approved international standards from your national member body or directly from ISO (http://www.iso.org).
The working group on Prolog standardisation is ISO/IEC JTC1/SC22/WG17 (http://www.sju.edu/~jhodgson/wg17/).
Convenor of WG17: Ulrich Neumerkel (
Further literature: "Prolog: The Standard (Reference manual)", P. Deransart, A. Ed-Dbali, L. Cervoni, Springer Verlag (1996). Extra information can be found on http://pauillac.inria.fr/~deransar/prolog/docs.html
http://www-2.cs.cmu.edu/afs/cs.cmu.edu/project/ai-repository/ai/lang/prolog/doc/standard/ contains the December 1991 draft, the March 1993 draft, Michael Covington's summary of it, and Richard O'Keefe's 1984 Prolog standard draft.
http://www.complang.tuwien.ac.at/ulrich/iso-prolog/ ISO Prolog works and related material by the convenor of WG17.
For questions about the standard, use this newsgroup or Stackoverflow.
11. How does the WAM (Warren Abstract Machine) work? How do I write a WAM-based compiler or a WAM emulator?
Reportedly the best tutorial is Hassan Ait-Kaci's book "Warren's Abstract Machine: A Tutorial Reconstruction" (MIT Press, 1991). The book is out of print, and available online at http://wambook.sourceforge.net.
12. Is there a WWW page on logic programming?
A collection of artifacts from logic programming languages beginning with Marseille Prolog is available from http://www.softwarepreservation.org/projects/prolog/index.html
A large amount of Prolog code is available from the CMU AI Repository: http://www.cs.cmu.edu/afs/cs/project/ai-repository/ai/lang/prolog/0.html
Recently, Stackoverflow has become a valuable resource for Prolog questions and answers: http://stackoverflow.com/questions/tagged/prolog
Another community resource is the #prolog IRC channel on irc.libera.chat.
13. Can I do Internet/WWW programming with Prolog?
Prolog is very suitable for this task. Several commercial and free implementations include special support for it. A page specifically on this topic (including some tutorials) is maintained at http://www.clip.dia.fi.upm.es/lpnet/lpnet.html. A public-domain library exists (PiLLoW) for several popular Prolog systems which helps in the task. See: http://www.clip.dia.fi.upm.es/Software/pillow/
14. Is there a WWW page with some tutorials on Prolog?
Adventure in Prolog: http://www.amzi.com/AdventureInProlog/advfrtop.htm
On-line guide to Prolog Programming: http://kti.ms.mff.cuni.cz/~bartak/prolog/index.html
Prolog Programming, A First Course: http://computing.unn.ac.uk/staff/cgpb4/prologbook/book.html
Learn Prolog Now!: http://www.learnprolognow.org
15. How do I edit Prolog code?
Emacs and VIM ship with basic support for Prolog. A much improved Emacs mode is maintained by Stefan Bruda and available from https://bruda.ca/emacs/prolog_mode_for_emacs
Logtalk ships with various editing services for many common editors, also usable for Prolog.
SWI Prolog has a built-in Emacs clone called PceEmacs. There are also Emacs definitions that let you evaluate embedded queries: https://www.metalevel.at/ediprolog/. An SWI Prolog programming environment suitable for schools is available from http://lernen.bildung.hessen.de/informatik/swiprolog/indexe.htm
A Prolog plug-in for the "Eclipse"-IDE is available from: http://eclipse.ime.usp.br/projetos/grad/plugin-prolog/index.html
A sophisticated integrated editing and teaching environment with declarative debugging, termination analysis and many visualisations is available from http://www.complang.tuwien.ac.at/ulrich/gupu/
16. How do I publish Prolog code?
Thank you to all the people who helped put together the first version of this FAQ, and everyone who has contributed to it over the years. Special thanks to John Dowding for suggesting a good format for the list, and to Chris Moss, Dag Wahlberg, and Mark Kantrowitz for their work on the Prolog Resource Guide.
Special thanks to Jamie Andrews, Dirk-Jan Faber and Remko Troncon, who have been maintaining and posting the FAQ in the past.