Prolog Notes

Some notes taken while working on Prolog (mostly SWI-Prolog)

A Tradition

From The Fifty-three Stations of the Tōkaidō by Utagawa Hiroshige, 1832.

The Logic Programming Landscape

So many modeling languages which are also programming languages, all a bit different.

Missed in the above:

• αProlog (Currently frozen?)
• GOLOG (Ancient, based on Situation Calculus. What's the relationship to LPS?)
• MProlog (PDF) for Modal Logic
• NProlog: An extension of prolog with hypothetical implication.
  • part 1
  • part 2
• HYPROLOG A Logic Programming Language with Abduction and Assumptions
• GOAL Agent Programming Language
• LogicBlox
• Datalog
• Logical Frameworks
• Markov Logic Networks -- This seems to be hot right now
• Lambda-Prolog: A pragmatic reconstruction of Lambda-Prolog
• There should be something here on implementation of more general theorem provers using the very restricted top-down theorem prover (or rather, "enumerating consequence checker") of Prolog. And how do you direct search in a theorem prover anyway? The NP desert is not for the faint of heart.

What is Prolog? In a 2012 paper by Peter Van Roy, Programming Paradigms for Dummies: What Every Programmer Should Know, the following diagram can be found on page 13:

Journals

Lest I forget:

• Theory and Practice of Logic Programming (Cambridge UP)
• The Journal of Logic Programming (Elsevier)

Notes

• Example code for some standard problems
  • Prolog implementations for Fibonacci Number computation (code is tilted towards SWI Prolog though)
  • A discussion of a "Prolog Database" operation
  • Various code snippets (testing predicates found in the SWI-Prolog manual)
• Having to do with programming constructs, some of which are specific to Prolog or to SWI-Prolog
  • foldl and foldr in Prolog
  • findall/3
  • Attributed Variables (an addendum to the SWI-Prolog manual page with new code)
  • Delimited continuations (to be continued!)
  • CHR: Constraint Handling Rules (there is nothing here yet)
  • DCGs: Definite Clause Grammars (just some work in progress)
  • Explaining dif/2 (but it's actually very simple in the end)
  • Exceptions (exceptions are useful, but the ISO standard exceptions are open to improvement)
    • Catch with backtrace
    • Throwing ISO standard exceptions
    • Problems with the ISO standard exception terms
    • Throwing in style: collecting exception specs in one place of the code
    • Example code to verify predicate arguments
    • And also: Conditions à la Lisp as alternative/complement to exceptions
  • The maplist/N predicates
  • Predicates dealing with I/O and printing (it all started with this...)
  • Predicates for analyzing/constructing terms
  • The use of the caret ^ in bagof/3, setof/3
  • SWI-Prolog string modes
  • How to load a library (the lynx library in this case)
• Having to do with generally explaining Prolog
  • "Byrd Box Model"
  • Depicting Terms (needs review)
  • Prolog list processing idioms
  • The concept of a "Prolog variable" (needs review once more)
  • Difference Lists (another one that is actually very simple in the end)
  • Prolog data types (somewhat specific to SWI Prolog)
    • Code to tag a Prolog term according to the data type decision tree: tagging.pl
• Having to do with JPL, the Java-Prolog Bridge
  • Some test code
• Having to do with general questions
  • Some notes on the Logic (Prolog is said to be based on classical logic, but is this really true?)
  • Some notes on the Truth Values (Prolog is said to be based on two-valued logic, but is this really true, or advised?)
  • Map of the Logic Programming landscape (actually quite detailed; shown above)
  • Map of the Rule-based Systems landscape (first try)
• Freestyle Notes, undigested
  • About Predicate Structure
  • Salvaging a term out of a dropped search branch
  • Better type tests

Code grabbag

Some predicates which may be of general use can be found in the Code grabbag

External Resources

• The first page of the SWI-Prolog manual has a large comment with pointers to resources ... sometimes I add something to that comment.
• Extensive list at klaussinani's github account
• The Prolog Syntax Highlighting file for KDE (by Torsten Eichstädt), as used in the Kate editor
• Bug Hunting Toolbox Wiki Page at SWI-Prolog Discourse Site
• Frank Pfenning's Course on Logic Programming (Lecture Notes as one PDF ... 324 pages). Hardcore!
• Richard O'Keefe: An Elementary Prolog Library: Discussion about extending the ISO standard with a usable library.
• The Prolog dictionary by Bill Wilson
• The SWI-Prolog glossary aka. "Appendix D"
• Glossary of Logic Terms (PDF) by Marc Cohen

On YouTube: "The Power of Prolog" by Markus Triska

List of Markus Triska's "Power of Prolog" YouTube videos

Papers of Interest

Papers of interest (a small selection)

Packages of Interest

• https://github.com/shonfeder/tokenize - "A modest tokenization library for SWI-Prolog, seeking a balance between simplicity and flexibility."