[saosebastiao]

I'm a huge fan of the declarative programming paradigm, but outside of Regexp and SQL and a handful of other DSLs, it's dead. Its death should be a case study in Open Source strategy: It died because it became boring before it became useful. SQL and Regexp have stuck around because they did something useful immediately.

I think that any future that the Declarative paradigm has within general purpose languages is the kind applied by compilers. For example, x = (a + b) - a can be reduced to x = a or even eliminated altogether with subsequent in-scope references to x being replaced with a. Another example is dead code elimination. These forms of declarative let you use an imperative or functional language immediately but gently introduce you to declarative benefits without having to deal with all the mind bending that is necessary to optimize pure declarative code.

[segmondy]

You are very mistaken. Prolog is still very much alive. You can find us on ##prolog in freenode. You can build a web application with prolog. When the 2048 madness was going on, I implemented in prolog in about 200 lines in 2 hours and I had about 3 weeks of prolog under my belt at that time. It's a very powerful concept. I didn't have to figure out the how to implement it, I just broke 2048 down into rules, declared it, and bam, I had a game.

[jroesch]

Prolog is an interesting exercise and occasionally useful as a tool, but most implementations leave a lot to be desired as a general purpose programming language. An example of this is SWIPL's 3 string types and their crazy behavior. You are also stuck in a first order language that is essentially pure, and have no abstractions for common patterns except meta programming which makes code even more difficult to reason about.

That being said I love having logical variables and I would love having them in other situations.

[singold]

How/where do you recommend to learn prolog? The concept looks really interesting and useful, at least for me.

[mindcrime]

There are a lot of good Prolog resources on the web. I gathered up a little list some time ago. You can find it here:

http://fogbeam.blogspot.com/2013/05/prolog-im-going-to-learn...

[saosebastiao]

I never said it wasnt useful, I said that it was dead...much in the same sense as COBOL. I use datalog and constraint programming extensively, but I'm a black sheep.

[segmondy]

It's not dead, until no one is using it. You can say APL is dead and I might believe you. So long as there's still people using prolog or other form of logic programming. It's not dead, all it needs is one killer application and everyone will jump on it. Erlang's popularity has surged since Whatsapp got acquired. Lots of people are learning about Erlang's root from Prolog and likewise getting somewhat curious about Prolog.

I might be wrong, but I think where the logic community failed is in taking advantages of multiple processors. Goals can be broken down and shared across multiple core/processors. So without changing code, the same program can be parallelized. It's just seems no one has implemented it yet.

[seanmcdirmid]

APL is far from dead, there is a lot of living legacy code and old timers with APL skills still actively using it commercially.

Prolog on the other hand...I'm not aware of any commercial projects actively using it, but it is still alive as a hobbyist/learning language.

[Solarsail]

Well, if you're only looking for logic languages instead of Prolog itself, then there's http://www.princexml.com/ written in Mercury.

[seanmcdirmid]

Of course. Datalog also gets alot of use in industry.