[macosxnerd101]

This week's challenge is Prolog, a logic-based programming language. Prolog is a declarative language which was originally designed for natural language processing, though has been used in the fields of artificial intelligence, theorem proving, games, and control systems. Rather than utilizing formal control-flow statements, Prolog allows for the definition of constraints and rules, with queries used to determine the result. Prolog also does not support formal looping, requiring recursion to implement iteration. In addition, Prolog supports higher-order programming, as well as dynamic and meta-programming, with many facilities for reflection.

Getting Started
There are a number of Prolog implementations, both commercial and for free, for various operating systems, including DOS, Windows, Mac OS, Linux, and Unix. There are also Prolog implementations for the JVM.

Some of these implementations include:

• GNU Prolog
  
• JTrolog
  
• B-Prolog

For a complete list of Prolog implementations, see the Wikipedia article

Resources and Tutorials

• The Free Country Prolog Tutorials
  
• Adventures in Prolog
  
• Prolog Programming Guide

Ideas

• Logic Puzzle Solver
  
• Artifial Intelligence program to play a game against a human

[brianarn]

Prolog is a fascinating language. I had exposure to it around eight or nine years ago, as part of my CS degree at UNM. Don't know if it's still a part of 451, but I'm glad it was then (Java was too, the core [123]51s were still C++ at the time).

Prolog is also covered in Seven Languages in Seven Weeks, which basically looks to be a self-driven version of that class. It hits some other languages too, and while I haven't read it myself, I might buy it this week, as they've got a special going, use the coupon code 'turkey' to get 40% off most all of their stuff.

Seriously, if you haven't played in Prolog before - take a little time and experiment. It's such a different approach from other languages, with some fascinating and fun results. Worth playing a bit.

[mostyfriedman]

I love prolog, one of my favorite programming languages.

[mostyfriedman]

this is a snippet i had, its nothing fancy, just shows how to permute a list in prolog, I just wanted to post it to show everyone how small the implementation is compared to any language.

delete(X, [X|T], T).

delete(X, [H|T], [H|S]):-
	delete(X, T, S).


permutation([], []).

permutation([H|T], R):-
	permutation(T, X), delete(H, R, X).

written in SWI-prolog.

This post has been edited by mostyfriedman: 22 November 2010 - 06:47 PM

[Tom9729]

SWI prolog is the best one that I've tried.

Here is a rather naive implementation of quicksort that I wrote for my programming languages class project...

% Tom Arnold <tarno1@brockport.edu>
partition(_, [], [], []).
partition(Pivot, [Item|List], Left, Right) :-
	Item >= Pivot,
	partition(Pivot, List, Left, NewRight),
	append(NewRight, [Item], Right), !.
partition(Pivot, [Item|List], Left, Right) :-	
	partition(Pivot, List, NewLeft, Right),
	append(NewLeft, [Item], Left), !.

quicksort(List, SortedList) :-
	length(List, ListLength),
	ListLength =< 1,
	SortedList = List.
quicksort([Pivot|Rest], SortedList) :-
	partition(Pivot, Rest, Left, Right),
	quicksort(Left, SortedLeft),
	quicksort(Right, SortedRight),
	append(SortedLeft, [Pivot], L1),
	append(L1, SortedRight, SortedList).