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https://github.com/triska/the-power-of-prolog

Introduction to modern Prolog
https://github.com/triska/the-power-of-prolog

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Introduction to modern Prolog

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README 

        
# The Power of Prolog



## Introduction to modern Prolog



Prolog is a **programming language** that is rooted in

formal logic. It supports *search* and *unification*

as built-in features. Prolog allows us to elegantly solve

many tasks with short and general programs.



[*A Tour of Prolog:*](https://www.metalevel.at/prolog/videos/tour) [![A Tour of Prolog](prolog/videos/t_tour.png)](https://www.metalevel.at/prolog/videos/tour)



The goal of this material is to *bridge the gap* between the

great traditional Prolog textbooks of the past and the language

*as it currently is*, several decades after these books

were written. You will see that many limitations of the past are

no longer relevant, while several new constructs are now of great

importance even though they are not yet covered in any available

Prolog book.



## Reading this book



This book is *self-hosting*: It includes an HTTP server that lets

you browse most of the content locally. When you access files that are

*not* locally available, it redirects to their online versions.



You need [Scryer Prolog](https://github.com/mthom/scryer-prolog)

to run it. For example, to spawn the server on port 6012, use:



    $ scryer-prolog -g "server(6012)" server.pl



Then, direct your browser to:



   http://localhost:6012/prolog



If you are new to Prolog, read the chapters in order for a

self-contained exposition of many important language features. If you

already have some experience with Prolog and would like to learn more

about more recent aspects, I recommend you start with the chapter on

[integer arithmetic](https://www.metalevel.at/prolog/clpz) and

proceed with the chapters it links to.



## About this book



The latest version of this book is always available from:



**https://www.metalevel.at/prolog**



I will periodically synch this repository with new material as it

becomes available.



I started writing this book in 2005, when I was a student of

Ulrich Neumerkel in Vienna. A collection of

[Prolog meta-interpreters](https://www.metalevel.at/acomip/)

formed the first chapter.



To run the code examples, you can use every Prolog implementation that

conforms to the Prolog ISO standard and provides the following

conforming extensions:



- Definite Clause Grammars (DCGs)

- constraints like `dif/2` and declarative integer arithmetic

- alternative execution strategies such as SLG resolution.



A *conforming* extension is a language feature that would not cause

any ambiguity or contradiction if it were added to the Prolog

standard, ISO/IEC 13211. Notably, a conforming extension

*must not* change the meaning of Prolog text which conforms to

the standard. Each of the above features can be added to every

Prolog system in a conforming manner, as exemplified by the

following recommended Prolog systems:



- [SICStus Prolog](https://sicstus.sics.se/)

  A state-of-the-art, ISO standard compliant, Prolog system.

- [Scryer Prolog](https://www.scryer.pl)

  A modern Prolog implementation written mostly in Rust.

- [GNU Prolog](http://www.gprolog.org/)

  A free Prolog compiler with constraint solving over finite domains.



In the example code, I assume that the Prolog flag `double_quotes` is

set to the value `chars` so that strings in double-quotes are

interpreted as lists of *characters*. This was the case in the

original Prolog implementation, Marseille Prolog, and is already the

default value in the four newest Prolog implementations,

[Scryer Prolog](https://github.com/mthom/scryer-prolog),

[Tau Prolog](https://github.com/tau-prolog/tau-prolog),

[Trealla Prolog](https://github.com/trealla-prolog/trealla) and

[ichiban/prolog](https://github.com/ichiban/prolog). It is to be hoped

that other Prolog systems will also adopt this setting to make

string processing with Prolog more convenient.



In some cases, slight modifications to code snippets may be necessary

to adjust for different libraries or small variations. See your Prolog

system's manual, or ask on Stackoverflow and `comp.lang.prolog`

for more information.



## On teaching Prolog



Prolog is an interesting programming language: It has a *pure*

monotonic core, and it also has features that are

called *impure*. You, the programmer, must decide in which subset

of the language you want to program.



In a sense, programming in Prolog is like writing a poem: You can

achieve great effects by writing under stringent constraints.

In Prolog, you often get the best results by restricting

your work to the pure core of the language. As long as

you do this, you can benefit from strong logical properties which let

you reason about your programs in systematic ways that are not

available in most other programming languages.



In the past decades, many pure features have become widely available

in Prolog systems. This book explains many of these new features,

and shows you how you can use them to achieve general and efficient

Prolog programs.



Currently, new pioneers are arising: The first instructors who use

this book in their courses! For example:



- As of 2018, Norbert Zeh is using *The Power of Prolog* in

  [CSCI 3136: Principles of Programming

  Languages](https://web.cs.dal.ca/~nzeh/Teaching/3136/index.html) at

  Dalhousie University in Canada.

- As of 2018, Andrej Bauer is using *The Power of Prolog* in his

  specialist elective course [Principles of Programming

  Languages](https://ucilnica.fri.uni-lj.si/course/view.php?id=67) at

  the University of Ljubljana in Slovenia.

- As of 2018, José A. Alonso Jiménez is using *The Power of Prolog* in

  his [Seminario de Lógica

  Computacional](https://www.glc.us.es/~jalonso/SLC2018/index.php/Documentaci%C3%B3n)

  at the Universidad de Sevilla in Spain.

- As of 2019, Adam Dingle is using *The Power of Prolog* in

  [Non-Procedural

  Programming](https://ksvi.mff.cuni.cz/~dingle/2019/npp/npp.html) at

  Univerzita Karlova in the Czech Republic.

- As of 2019, Dylan Schwesinger is using *The Power of Prolog* in

  [Artificial

  Intelligence II](http://csitrd.kutztown.edu/~schwesin/spring19/csc548/index.html)

  at Kutztown University in the United States of America.

- As of 2020, Andrea Schwertner Charão is using *The Power of Prolog* in

  [Paradigmas de Programação](https://github.com/AndreaInfUFSM/elc117-2020a/)

  at the Federal University of Santa Maria in Brazil.

- As of 2020, Alejandro Guerra Hernández is using *The Power of

  Prolog* in [Programación para la Inteligencia

  Artificial (PIA)](https://www.uv.mx/personal/aguerra/pia/) at

  the Universidad Veracruzana in Mexico.

- As of 2021, Ilkka Kokkarinen is using *The Power of Prolog* in

  [CCPS 721 Artificial

  Intelligence I](https://github.com/ikokkari/AI) at the G.

  Raymond Chang School of Continuing Education,

  Ryerson University, in Canada.

- I hope you are next!




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