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The Power of Prolog

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Re: The Power of Prolog

#141

Post by bpyne »

YeGoblynQueenne wrote: post #114
fizixer wrote: post #2

Roughly half the 'power of prolog' comes from the 'power of logic programming' and prolog is by far not the only logic programming language, e.g., - You can do logic programming using minikanren in scheme. (you can also extend the minikanren system if you find a feature missing). - Minikanren was implemented in clojure and called core.logic. - It was also ported to python by Matthew Rocklin I think, called logpy. - T…

>> Roughly half the 'power of prolog' comes from the 'power of logic programming' and prolog is by far not the only logic programming language, e.g., It is also by far the most popular logic programming language, in terms of the number of users and the number of different interpreters. It's a bit like LISP and functional languages, although of course functional programming has been adopted far more than logic program…

Out of curiosity, have you used Curry? The combination of logic and functional paradigms in one language is intriguing to me, but I have no time (right now) to play with it.

Re: The Power of Prolog

#142

Post by naasking »

StreamBright wrote: post #137
sordina wrote: post #23

Earlier quoted context omitted.

Check out https://en.wikipedia.org/wiki/Horn_clause You can read this as two statements: "The length of a list is 0, if the list is empty." "Otherwise, if the length of a list Ls is N0, and N is N0 + 1, and N is greater than 0, then Ls with an additional element is of length N.

Excellent. How am I supposed to interpret this, or being able to write code? Even Erlang is much more readable and understandable at the first sight. :)

That's because Erlang is still a traditional imperative programming language, so it just slightly tweaks what you're already used to. Logic programming is completely different.

Re: The Power of Prolog

#143

Post by bloaf »

tom_mellior wrote: post #86
lacampbell wrote: post #66

Earlier quoted context omitted.

ah! backtracking. combinatorial optimisation would be incredibly useful for me. if prolog is indeed backtracking as a language I definitely need to look into it.

It is indeed backtracking as a language, but you don't get optimization entirely for free. The backtracking part only means that you can write down a problem that has multiple solutions and get Prolog to enumerate those solutions using its default order. If the set of solutions is small enough, you can enumerate all of them and pick out the best one, or have it enumerate them until you get one that is good enough. Bu…

Would it work well for algorithms like A*, or other quazi-AI problems that crop up in games?

Re: The Power of Prolog

#144

Post by vram22 »

hexmiles wrote: post #19

i have always trouble understaing prolog, lot of guide online seem to just tackle the syntax or assume you already know a lot of logic programming, for example the first example in the link ( https://www.metalevel.at/prolog/facets ): list_length([], 0). list_length([_|Ls], N) :- N #> 0, N #= N0 + 1, list_length(Ls, N0). i don't undestand it, i read the segment describing it multiple time but i still don't get it, and…

I see there are multiple good answers already, but I'll just add my 2c - which answers from a different angle, sort of (though partially similar to some of the other answers). It may help, if you understand recursive calls to functions, and an imperative language like Python - the examples are in Python:

Recursive computation of simple functions:

https://jugad2.blogspot.in/2016/03/recursive-computation-of-...

The first example shown is for computing the length of a list, recursively.

Edit: To make it clear, my example uses an imperative approach, while your Prolog example uses a declarative approach. As the excellent comments by carapace and kevhito show, the two approaches are different. Just that my example may help you to get the solution used. But in Python, we tell the interpreter how to compute the length of a list. In Prolog, it is sort of as though we tell the interpreter what we want it to find out (a goal), and give it some facts / properties and rules to help it do that. It then does that, using its inference engine.

HTH.

Re: The Power of Prolog

#146

Post by mark_l_watson »

FabHK wrote: post #138
mark_l_watson wrote: post #112

I bookmarked this. I have been revisiting my own programming history. I used Prolog a lot in the 1980s, partially because I was influenced by the ill-fated Japanese 5th generation project. A few weeks ago I pulled my old Prolog code experiments from an old repo. Prolog is a great language for some applications, and Swi-Prolog has some great libraries and sample programs. I also have used Common Lisp a lot since the 1…

You had version control systems in the 80s? I had cassette tapes and later 5 1/4 inch floppy disks!

I moved everything to svn, and later to git repos.

I actually had 8" floppy disks on my Xerox Lisp Machine. An unnatural size for floppy disks!

Re: The Power of Prolog

#147

Post by fizixer »

YeGoblynQueenne wrote: post #115
fizixer wrote: post #2

Roughly half the 'power of prolog' comes from the 'power of logic programming' and prolog is by far not the only logic programming language, e.g., - You can do logic programming using minikanren in scheme. (you can also extend the minikanren system if you find a feature missing). - Minikanren was implemented in clojure and called core.logic. - It was also ported to python by Matthew Rocklin I think, called logpy. - T…

>> EDIT: ILP at an advanced level starts making connections with PGMs (probabilistic graphical models) and hence machine learning, but its a long way to go for me (in terms of learning) before I start to make sense of all these puzzle pieces. ILP is machine learning, it's a family of algorithms that learn logic programs usually from structured data. So for instance, table rows go in one end and Prolog clauses come ou…

Thanks for the comment and references. Good luck with your PhD program.

> ... Connections with PGMs... hmm, not sure what you mean.

What I meant is that ILP, PGM, HMM, are some of the topics that were being explored as an extension to GOFAI in the 1990s and first half of 2000s before the 2006 breakthrough results by Hinton which drastically shifted the focus towards NNs, Deep learning, etc.

Essentially these topics were being explored as a result of the slow realization that logic is not enough to represent highly complex systems, and there is a need to move towards a hybrid of logical and probabilistic approaches.

I'm keenly interested in these areas but currently busy with graduate work related to numerical analysis and scientific computing. In our circles 'adaptive' is the big word, and there is attempt to utilize AI/ML methodologies in scientific simulation, but it's at a very early stage. Once my work is finished, I hope to get more involved in ML related research and applications.

Re: The Power of Prolog

#148

Post by tmaly »

Karrot_Kream wrote: post #20
fizixer wrote: post #2

Roughly half the 'power of prolog' comes from the 'power of logic programming' and prolog is by far not the only logic programming language, e.g., - You can do logic programming using minikanren in scheme. (you can also extend the minikanren system if you find a feature missing). - Minikanren was implemented in clojure and called core.logic. - It was also ported to python by Matthew Rocklin I think, called logpy. - T…

Not really. I use SWI Prolog for a lot of personal projects (that actually see QPS no less) and there's a lot more to it than that. SWI gives you: good debugging support (with trace and spy), hooks into the Prolog database (with asserta/z and retract), optimized implementations of difference lists, online help, and so much more. Don't even get me started on its amazing DCG support that makes Regex feel like a Neolith…

I have used SWI Prolog in a professional setting to solve a very complex problem in a short deadline. It is definitely a tool to have in your toolbox.

Re: The Power of Prolog

#149

Post by tom_mellior »

bloaf wrote: post #143
tom_mellior wrote: post #86

Earlier quoted context omitted.

It is indeed backtracking as a language, but you don't get optimization entirely for free. The backtracking part only means that you can write down a problem that has multiple solutions and get Prolog to enumerate those solutions using its default order. If the set of solutions is small enough, you can enumerate all of them and pick out the best one, or have it enumerate them until you get one that is good enough. Bu…

Would it work well for algorithms like A*, or other quazi-AI problems that crop up in games?

Yes, but you shouldn't expect it to have much more magic support for this kind of algorithms than other languages.

Re: The Power of Prolog

#150

Post by carapace »

Karrot_Kream wrote: post #88
carapace wrote: post #31

Earlier quoted context omitted.

I'd like to hear that story, when you get the chance. ;-)

Sure and thanks for the wait! To give a bit of background: I run a service for some folks that allows them to get status messages. Some of my users wanted stats on the kinds of messages they received. My first implementation was quick and dirty: shell scripts which would run filters and aggregations through combinations of grep, sort, and uniq. Eventually as more demands came in with different types of functionality,…

Cheers. :-)
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