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Prolog, and Constraint Programming especially are great to have in your toolbox. I’ve done research in the field for years, and my job in the industry today is

Prolog, and Constraint Programming especially are great to have in your toolbox. I’ve done research in the field for years, and my job in the industry today is writing Prolog. There are real issues with Prolog: - no proper module nor package system in the modern sense. - in large code bases extra-logical constructs (like cuts) are unavoidable and turn Prolog code into an untenable mess. SWI prolog has single-sided unification guards which tackle this to a degree. - lack of static and strong types makes it harder to write robust code. At least some strong typing would have been nice. See Mercury as an example of this. All being said, Prolog is amazing, has a place in the future of programming, and gives you a level-up understanding of programming when you get how the types in every OO program is a Prolog program itself.

ecshafer 2y ago
There are a lot of problems that Prolog / Constrain programming will solve very elegantly, and much more easily than imperative languages. I think constraint based programming is seriously under used in the industry, and too many programmers are unaware or unable to write constraint based code. I have always hoped to have just a constrain based programming subsystem in a lot of languages, for those niche cases.
ToucanLoucan 2y ago
Maybe it's just me but I see a lack of a package manager as a massive, massive pro. I can't stand how seemingly every language has a package manager which requires it's own installation and you have to learn how to use THAT thing and then you need some library off github that does some minor task really well but you can't just download the fucking code, you have to import it via, idk, the Fork-Lyft manager which requires Python 3.3 and the PillJump framework and it's just like, I just want a fucking function to parse JSON, I don't want to saddle my system with 600 MB of shit I don't need. Old_man_yells_at_cloud.jpg
- qu1j0t3 2y ago
  don't confuse "module system" with "package manager"
- phailhaus 2y ago
  You can always just download the code, nobody's forcing you to use a package manager. It just turns out that unless you want to spend most of your life building and fixing other people's code, it's much easier to use the package manager. The inefficiency is the price we pay, but it's worth it.
- duranga1234 2y ago
  Me too! I absolutely see a lack of package manager as a pro. I also hate to saddle anything with 600MB I don't need. 100% agree. I would go as far as to say that Prolog is more a problem solving language rather than a system building language. Package managers and module systems are for modularization of big systems. You don't need that when solving small recurrent problems. Furthermore, lack of them forces you to avoid dependencies, that most of the time would end as technical debt. IMHO.
radomir_cernoch 2y ago
You write Prolog code for a living? Where? Do you happen to have a story to share? I'm very curious.
- BJones12 2y ago
  I suspect that his work is related to this: https://www.tacton.com/products/tacton-cpq/configurator/ https://www.tacton.com/products/tacton-cpq/configurator/
  - gorkempacaci 2y ago
    Yes :)
- gorkempacaci 2y ago
  Yes :) we make software that helps sell complex products (If your product has a million options and takes up a whole factory floor you can’t just have a series of dropdowns)
  - _glass 2y ago
    Thanks for the insight, Görkem! I was always thinking CPQs make a really good use case. We had so many problems with performance, not your product, CPQ is becoming a standard software for pricing contracts.
kibwen 2y ago
> when you get how the types in every OO program is a Prolog program itself "Any sufficiently complicated type system contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Prolog."
- Arch-TK 2y ago
  Any sufficiently complex type system is indistinguishable from an esolang.
tannhaeuser 2y ago
I'd advise to not use Prolog as general-purpose programming language, but as an embedded DSL or as a service for the part it's really suited for (if your app involves exploration and search over a large combinatorical space in the first place, such as in discrete optimization in industry, logistics, and finance). You really don't need yet another package manager and pointless premature modularization for modelling your business domains in optimization.
- inkyoto 2y ago
  I concur, Prolog particularly excels at being an advanced configuration, embeddable DSL that allows one to express system configurations that would otherwise be not easily possible using a bespoke configuration language or a format. I have used an embedded Prolog core to express complex installation configurations in the past with a great success, and I would do it again for the right problem space.
  - hosh 2y ago
    The cluster autoscaler in Kubernetes uses a constraint solver. It's translating configuration against dynamic, and changing state within the cluster. Using something like an embedded Prolog or miniKenran as the core of a Kubernetes operator is something I've wanted to try my hands on.
- jimbokun 2y ago
  To me this makes Prolog sound like a tool to reach for similar to SQL. Specialized language for asking specific kinds of search or query over your data.
  - gorkempacaci 2y ago
    Indeed Prolog programs are also called databases sometimes. Some things Prolog can do over SQL: - infinite data defined by recursive predicates - flexible data structures (think JSON but better, called complex terms) and a way to query them (called unification algorithm) - execution strategy fine-tuned for reasoning (called resolution algorithm). You can do this with SQL but you’d have to formalize things using set operations and it’d be very very slow. On the other hand, SQL can query plain data very very fast.

ecshafer 2y ago

There are a lot of problems that Prolog / Constrain programming will solve very elegantly, and much more easily than imperative languages. I think constraint based programming is seriously under used in the industry, and too many programmers are unaware or unable to write constraint based code. I have always hoped to have just a constrain based programming subsystem in a lot of languages, for those niche cases.

ToucanLoucan 2y ago

Maybe it's just me but I see a lack of a package manager as a massive, massive pro. I can't stand how seemingly every language has a package manager which requires it's own installation and you have to learn how to use THAT thing and then you need some library off github that does some minor task really well but you can't just download the fucking code, you have to import it via, idk, the Fork-Lyft manager which requires Python 3.3 and the PillJump framework and it's just like, I just want a fucking function to parse JSON, I don't want to saddle my system with 600 MB of shit I don't need. Old_man_yells_at_cloud.jpg

qu1j0t3 2y ago
don't confuse "module system" with "package manager"
phailhaus 2y ago
You can always just download the code, nobody's forcing you to use a package manager. It just turns out that unless you want to spend most of your life building and fixing other people's code, it's much easier to use the package manager. The inefficiency is the price we pay, but it's worth it.
duranga1234 2y ago
Me too! I absolutely see a lack of package manager as a pro. I also hate to saddle anything with 600MB I don't need. 100% agree. I would go as far as to say that Prolog is more a problem solving language rather than a system building language. Package managers and module systems are for modularization of big systems. You don't need that when solving small recurrent problems. Furthermore, lack of them forces you to avoid dependencies, that most of the time would end as technical debt. IMHO.

radomir_cernoch 2y ago

You write Prolog code for a living? Where? Do you happen to have a story to share? I'm very curious.

BJones12 2y ago
I suspect that his work is related to this: https://www.tacton.com/products/tacton-cpq/configurator/ https://www.tacton.com/products/tacton-cpq/configurator/
- gorkempacaci 2y ago
  Yes :)
gorkempacaci 2y ago
Yes :) we make software that helps sell complex products (If your product has a million options and takes up a whole factory floor you can’t just have a series of dropdowns)
- _glass 2y ago
  Thanks for the insight, Görkem! I was always thinking CPQs make a really good use case. We had so many problems with performance, not your product, CPQ is becoming a standard software for pricing contracts.

kibwen 2y ago

> when you get how the types in every OO program is a Prolog program itself "Any sufficiently complicated type system contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Prolog."

Arch-TK 2y ago
Any sufficiently complex type system is indistinguishable from an esolang.

tannhaeuser 2y ago

I'd advise to not use Prolog as general-purpose programming language, but as an embedded DSL or as a service for the part it's really suited for (if your app involves exploration and search over a large combinatorical space in the first place, such as in discrete optimization in industry, logistics, and finance). You really don't need yet another package manager and pointless premature modularization for modelling your business domains in optimization.

inkyoto 2y ago
I concur, Prolog particularly excels at being an advanced configuration, embeddable DSL that allows one to express system configurations that would otherwise be not easily possible using a bespoke configuration language or a format. I have used an embedded Prolog core to express complex installation configurations in the past with a great success, and I would do it again for the right problem space.
- hosh 2y ago
  The cluster autoscaler in Kubernetes uses a constraint solver. It's translating configuration against dynamic, and changing state within the cluster. Using something like an embedded Prolog or miniKenran as the core of a Kubernetes operator is something I've wanted to try my hands on.
jimbokun 2y ago
To me this makes Prolog sound like a tool to reach for similar to SQL. Specialized language for asking specific kinds of search or query over your data.
- gorkempacaci 2y ago
  Indeed Prolog programs are also called databases sometimes. Some things Prolog can do over SQL: - infinite data defined by recursive predicates - flexible data structures (think JSON but better, called complex terms) and a way to query them (called unification algorithm) - execution strategy fine-tuned for reasoning (called resolution algorithm). You can do this with SQL but you’d have to formalize things using set operations and it’d be very very slow. On the other hand, SQL can query plain data very very fast.