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Introduction to logic programming with Prolog

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Re: Introduction to logic programming with Prolog

#21

Post by gota »

chkte wrote: post #16

I know how to code in Prolog. How can I take profit of it, apart from my academic (undergraduate) interests? Can I build something in particular, can I look for specific jobs?

There are not that many companies using prolog code, but specialized AI companies still do. I've worked as a consultant programmer developing large decision-support systems for engineering projects and the bulk of the domain logic was written in prolog. Most operational stuff was in C++ or Python, still, so even in that project there were as many jobs for Python programmers as there were prolog programmers

You don't truly appreciate the declarative paradigm until you are able to describe (and find the best among) all billions of complex possibilities of configurations of nuts and bolts following all these engineering laws, practices and rules of thumb... in a hundred lines or less

I love Python and I'll introduce myself as a Python programmer, but part of me will always have a deep respect for prolog and how utterly awesome it is in the right context

Re: Introduction to logic programming with Prolog

#22

Post by pvinis »

legionth wrote: post #4

I hated it in university and hate it until this very moment. I get what this language is doing and why it is great for special usecases. But I can absolutly can not read code written in Prolog. Staring at 3 lines of code and not knowing what the hell it does, gives me nightmares till today. You can write a quicksort in a few lines. You can traverse over a tree very easily. But understanding these few lines takes me m…

I've had the opposite experience. In university and later, everytime I play with prolog, I love it. Some things make so much more sense when you write them this way, and it's not just the few very specific cases. When I learned about prolog and had the first couple of classes using it, I was delighted! Finally a language that works in a way my mind likes to think in.

I am not saying that one way or language is better than the other. But I'm saying that, like you are faster to rewrite in c or java, there are people that can rewrite or understand faster the other way. :)

Programming is fun!

Re: Introduction to logic programming with Prolog

#23

Post by mathetic »

Hendrikto wrote: post #20
mathetic wrote: post #18

Earlier quoted context omitted.

Ah, that's a problem with many facets. It is not that we can't come up with a logic language that is more declarative, it is just that telling the program everything about the universe is so damn dull. For example, ordering of your body predicates will often be based on what you think intuitively their sizes of solutions are going to be e.g. `plus(A,B,C), solution(C,X).` You know that plus is injective, so you put it…

I do not get why you mean by plus being injective. `plus(1, 2, C). C = 3.` `plus(0, 3, C). C = 3.` Isn't that a counterexample, showing how it is not injective?

Yes, I was thinking total with respect to _intuitive_ arguments, but wrote injective. Sorry.

Re: Introduction to logic programming with Prolog

#25

Post by simias »

legionth wrote: post #4

I hated it in university and hate it until this very moment. I get what this language is doing and why it is great for special usecases. But I can absolutly can not read code written in Prolog. Staring at 3 lines of code and not knowing what the hell it does, gives me nightmares till today. You can write a quicksort in a few lines. You can traverse over a tree very easily. But understanding these few lines takes me m…

Something tells me that it would probably be easier if this was your first programming language. Actually I expect that some would find this declarative style a lot more intuitive and natural.

But when you've spent many years writing imperative code it feels so alien. It reminds me of the first time I attempted to write Verilog, it's hard to break the mold and change the way you think about the flow of a program and how you construct algorithms. Eventually it clicked for me and Verilog though, so I expect with enough dedication one could do the same with Prolog.

Re: Introduction to logic programming with Prolog

#26

Post by pjmlp »

legionth wrote: post #4

I hated it in university and hate it until this very moment. I get what this language is doing and why it is great for special usecases. But I can absolutly can not read code written in Prolog. Staring at 3 lines of code and not knowing what the hell it does, gives me nightmares till today. You can write a quicksort in a few lines. You can traverse over a tree very easily. But understanding these few lines takes me m…

I love Prolog, to the point of having taken part in the Portuguese university national logic championship back in the 90's.

On our degree, we had three logic programming classes, starting from logic programming as pure math all the way to deep Prolog exercises.

Re: Introduction to logic programming with Prolog

#27

Post by vanderZwan »

tannhaeuser wrote: post #15
vanderZwan wrote: post #6

I've seen a few contalks about logic programming, read a few articles, and aside from the intellectual curiosity in itself I can see that it is very elegant in certain circumstances (although I lack the hands-on experience to feel what those circumstances are). Since doing a whole program in prolog isn't really practical for me, is there any way to use the logic programming paradigm in mainstream programming language…

The point of Prolog as a practical logic programming language really is that it is portable accross Prolog implementations based on ISO Prolog (and maybe prolog-commons API compatibility). If you're using a Prologish tool (a Java framework, say) that is not quite Prolog, then you're loosing the compatibility for very little gain IMHO. Applications domains I've used Prolog for: discrete planning, game logic, limited/r…

> The point of Prolog as a practical logic programming language really is that it is portable accross Prolog implementations based on ISO Prolog (and maybe prolog-commons API compatibility). If you're using a Prologish tool (a Java framework, say) that is not quite Prolog, then you're loosing the compatibility for very little gain IMHO.

I feel like I might be missing something obvious, but I'm not getting what the "compatibility" you refer to would give me in my specific situations? It looks like you're saying "if you write a Prolog program, it's compatible across Prolog platforms." Well, sure, but how is that fundamentally more portable situation than (for example) "if I have a logic programming framework in ES16, it works in all browsers that run modern JavaScript"?

If I'm specifically trying to do something in the browser (again, for example) and have a problem within that context where logic programming might be useful, having a way to use logic programming in JS makes more sense, doesn't it?

Re: Introduction to logic programming with Prolog

#28

Post by tr352 »

virgilp wrote: post #5

I find the section 5.3 from the paper "Out of the tar pit"[1] describes it very well: > It is for this reason that Prolog falls short of the ideals of logic programming. Specifically it is necessary to be concerned with the operational interpretation of the program whilst writing the axioms. I haven't heard of any approach that generalizes the goals of logic programming in a far better way. Is there any? (on specific…

What you're looking for is called answer set programming. It has pretty much replaced logic programming as a research focus, and a number of implementations exist.

Re: Introduction to logic programming with Prolog

#29

Post by yummy »

legionth wrote: post #4

I hated it in university and hate it until this very moment. I get what this language is doing and why it is great for special usecases. But I can absolutly can not read code written in Prolog. Staring at 3 lines of code and not knowing what the hell it does, gives me nightmares till today. You can write a quicksort in a few lines. You can traverse over a tree very easily. But understanding these few lines takes me m…

I don't think working with numbers is a strong side of Prolog. Quicksort in Haskell is also 3 lines, but it's totally readable. I can make use of functional programming in my daily life, but logic? Never. But think of the Zebra puzzle. In Prolog the solution is 100% declarative.

BTW, I hate Prolog too.

Re: Introduction to logic programming with Prolog

#30

Post by flavio81 »

pgtan wrote: post #19

I try to introduce my boy (12) in programming trough Scratch but still no big success. However, we solved recently two math homework exercises with Prolog (logic) and MetaPost (geometry) which caused some effect, so I'm thinking to deepen in that languages or may be switch to Logo as intermediate lisp like solution.

That is the best way to introduce computers to a kid: "let it do the hard work for you".

Logo used to be very popular for kids here in the '80s. I learnt Logo when i was 7, then i "progressed" over the years to Basic, C, Pascal, C++, Java, C#, Python and now, after about 28 years, Lisp. And now I realize Logo is close to Lisp in many ways and a far more powerful language than some of the ones I "progressed" to.

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