Frequently Asked Questions - comp.lang.prolog

Markus Triska (Mar. 2 2007 - ... )

Remko Troncon (Jan. 6 2002 - Mar. 2 2007)

Dirk-Jan Faber (Feb. 1 1999 - Jan. 6 2002)

Jamie Andrews (Aug 26 1992 - Oct. 16 1997)

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:

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 or contact

Sandro Etalle

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 (), 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.)

ALF (Algebraic Logic Functional language)
Amzi! Prolog + Logic Server
Aquarius Prolog 1.0
Argo Prolog v.1.1
  • Platforms: Solaris 1.x and HP-UX 9.x

  • Available: Unknown

  • Contact: Takao Doi

  • Platforms: Win32

  • Available:

  • 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.

B-Prolog 8.1
BinProlog 7.0
  • Platforms: Windows 95/98/NT, Linux and all major Unix platforms.

  • Available:

  • 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.

Brain Aid Prolog (BAP) v1.4
  • Platforms: Transputer systems

  • Info: BAP is a parallel prolog system for Transputer systems. Available under a Berkely style of copyright.

  • Platforms: Win32, UNIX

  • Available:

  • 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.

Ciao 1.4
  • Platforms: Linux, Win32 (95/98/NT), Solaris, SunOS, UNIX in general.

  • Available:

  • E-mail: Developers , Users

  • 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.

  • Platforms: UNIX

  • Contact: Daniel Diaz

  • Info: Constraint logic programming over finite domains. Requires GNU C v.2.4.5 or higher.

  • Platforms: UNIX

  • Contact: Yan Georget

  • Info: Requires GNU C (gcc) version 2.4.5. or higher.

  • Platforms: UNIX

  • Available: E-mail request from Joxan Jaffar .

  • Info: Constraint logic programming language, for academic and research purposes only.

  • Platforms: UNIX, MacOS X, Windows

  • Available:

  • 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

ECLiPSe Constraint Logic Programming System, subsuming Prolog.
IF Prolog V5.3
  • Platforms: Windows 95/98/NT/2000/XP, Linux, Solaris, AIX, HP-UX and other UNIX platforms

  • Available:

  • E-mail:

  • 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.

GNU Prolog
Jinni 2.27
  • Platforms: Java-based

  • Available:

  • Info: Multi-threaded, Java based Prolog interpreter with built-in networking, distributed blackboards and mobile code (inexpensive shareware licensing available).

  • Platforms: Java-based

  • 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.

  • Platforms: UNIX

  • Info: ICOT Free Software. Concurrent logic programming. Tested on Sparcs, DEC 7000, Gateway P5-60.

  • Contact:

LPA Win-Prolog, demo version
  • Platforms: Java

  • Info: Proprietary commercial ISO-Prolog Compiler in 100% Java support for web programming, XML, servlets, applets, standalones. Free evaluation license.

Modular SB-Prolog (= SB-Prolog version 3.1 plus modules)
  • Platforms: SPARC, DECstation, MIPS, HP 9000 series, Sun 3.

  • Info: Copy-lefted.

Open Prolog
Poplog Prolog
  • Platforms: Unknown

  • Available: On CompuServe in the AIEXPERT forum, interpreter and examples in PIE2.ZIP, documentation in PIEDOC.ZIP.

  • E-mail: Brent Ruggles

Scryer Prolog
Strawberry Prolog
SWI Prolog
  • 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.

  • Available:

  • 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.

Tau Prolog
  • Platforms: Windows 95/98/NT 4.0, plans for Windows 2000, Linux and Sun Solaris

  • E-mail:

Visual Prolog
  • Platforms: Win32

  • Available:

  • 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.

  • Platforms: UNIX

  • 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+

  • Available:

  • 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: UNIX-based platforms and Windows

  • Available:

  • 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

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.

ALS (Applied Logic Systems)
Amzi! inc.
Ciao, PiLLoW, WebDB, etc.
Expert Systems Ltd. (Prolog-2)
GNU Prolog
  • Formerly BIM ProLog

PDC Prolog
  • PDC Prolog is the succesor to Turbo Prolog and the predecessor to Visual Prolog.

ProLog by BIM
  • Currently MasterProLog

Trinc / Trinc-Prolog
Turbo Prolog
  • Turbo Prolog is the predecessor of PDC Prolog (see above).

Visual Prolog

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:


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 (), 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

  • "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.

Logic programming theory
  • "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

Expert Systems

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!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 (

The working group on Prolog standardisation is ISO/IEC JTC1/SC22/WG17 (


Further literature: "Prolog: The Standard (Reference manual)", P. Deransart, A. Ed-Dbali, L. Cervoni, Springer Verlag (1996). Extra information can be found on contains the December 1991 draft, the March 1993 draft, Michael Covington's summary of it, and Richard O'Keefe's 1984 Prolog standard draft. 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

12. Is there a WWW page on logic programming?

Yes, there is one by Jonathan Bowen; the URL is He invites us to mail him at with any relevant information for inclusion.

A collection of artifacts from logic programming languages beginning with Marseille Prolog is available from

A large amount of Prolog code is available from the CMU AI Repository:

Recently, Stackoverflow has become a valuable resource for Prolog questions and answers:

Another community resource is the #prolog IRC channel on

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 A public-domain library exists (PiLLoW) for several popular Prolog systems which helps in the task. See:

14. Is there a WWW page with some tutorials on Prolog?

Beginner level:
Intermediate to advanced level:

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

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: An SWI Prolog programming environment suitable for schools is available from

A Prolog plug-in for the "Eclipse"-IDE is available from:

A sophisticated integrated editing and teaching environment with declarative debugging, termination analysis and many visualisations is available from

16. How do I publish Prolog code?

Logtalk ships with support for various syntax highlighters, also usable for Prolog. These include support for Pygments (used e.g. on Trac and GitHub), Rouge (use e.g. in GitLab), GeSHi (used e.g. on Wikis), minted and texments LaTeX packages (e.g. source code listings), Google Code Prettify, Source-highlight, Highlight, SyntaxHighlighter, and SHJS (JavaScript highlighter for e.g. web pages).


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.