IIRC Rich wanted a name that has CLR and J in it - Clojure initially was officially to be supported on both .Net and Java stacks. Later he realized that keeping it completely compatible on both platforms is an uphill battle. CLR Clojure still exists, but it's not "an officially supported" runtime.
Scheduling, e.g., course scheduling - allocating rooms, professors, time slots while satisfying constraints; Product configuration systems - helping customers select compatible options for complex products; Genealogical research - querying family relationships and ancestry; Static analysis tools for code - finding bugs or verifying properties without execution; Medical diagnosis systems - inferring conditions from symptoms based on medical knowledge; Travel planning - finding optimal routes with multiple constraints; Legal reasoning systems - determining applicability of laws to specific cases; Natural language interfaces - parsing questions and generating appropriate database queries; Hardware verification - proving correctness of circuit designs; Puzzle solvers - Sudoku, crosswords, logic puzzles;
Basically anything that excels when declarative specification of relationships is more natural than imperative algorithms.
This all makes perfect sense. The gap I usually have - and I admit its probably something of a skill issue, I have relatively little formal CS background - is how these abstract declarations of rules are integrated into a product. The example code in projects like this is usually pretty dense and intangible.
Does anyone have good examples of open source codebases or reading material in this area? Lets imagine I have a set of complex business rules about the way a product can be configured and I want to use a logic programming language to enforce them, called from a web interface based on config data stored in a traditional relational database. Is that... a misunderstanding of how these things are to be used?
I've love a good book about how to bring tools and techniques for logical correctness into a Rails ecosystem... or similar language/framework for app dev. I love the promises many of logic languages make but can't rewrite existing applications in them wholesale and it seems like they're a poor fit for that anyways. How are people blending these worlds at large enterprises? Maybe the answer is that nobody really is yet, and thats what makes things like Clolog + Clojure so exciting?
FWIW I have no formal CS background whatsoever (maybe you shouldn't even listen to me on this matter), but if you want to gain some understanding of rule engines, you probably shouldn't start with core.logic or clolog (I have not looked into this project myself just yet, so my assumptions might be completely misleading) - core.logic imo good for complex constrains and relationships, it's based on miniKanren, but has quite steep learning curve, and not sure if it's worth the effort (as a starting point).
oakes/odoyle-rules is a forward-chaining rules engine with a more straightforward approach - for someone already familiar with Clojure, it should be fun to try out. Then maybe check out Clara Rules, if I'm not mistaken the lib is specifically designed for business rules processing. For understanding the theoretical pieces, you probably want to look into forward vs. backward chaining rule systems; pattern matching used in rules engines; understanding how to model domain rules declaratively; Rete algorithm (odoyle lib explains it and iirc links to the paper).
Awww, thank you. As a Clojurian, I aspire to be kind and helpful. The Clojure community is renowned for its friendly, coaching-oriented attitude. Anyone with questions (even those unrelated to Clojure) should absolutely reach out to Clojuristas — just go to http://clojurians.net and don't be shy.
I'm forever thankful for Clojure for reigniting my passion for programming, but particularly, I'm indebted to the many individuals in the Clojure community. Whenever I pose a question expecting just straightforward guidance or documentation links, I consistently receive profound, thought-provoking answers that surpass my expectations. Virtually every discussion I initiate with them ends up being incredibly educational, teaching me far more than I initially sought. I can confidently admit - yes, learning Clojure has made a better programmer out of me, but most importantly, it made me a better person.
Well the bigger question is how big does the system have to be to warrant breaking out a new technique, much less adding a new runtime or other large dependency.
Now, I have no direct experience with any of the common logical programming systems. I have familiarity.
But anytime I came upon anything that might justify such a system, the need just didn’t seem to justify it.
Talking less than 100 rules. Most likely less than a couple dozen. Stacking some IFs and a bit of math, strategically grouped in a couple aptly named wrapper methods to help reduce the cognitive load, and it’s all worked pretty well.
And, granted, if I had solid experience using these systems, onboarding cost would be lower.
Absolutely valid and befitting point - adding complexity without clear benefits never should be justified. Most (business) applications have ruleset logic for specific problems not exceeding a dozens of rules - regular code often works fine.
Logic systems tend to show the value when rules become complex with many interdependencies or non-linear execution patterns emerge, or rules change frequently or need to be defined at runtime; when you need explanation tools - e.g., why was this conclusion reached?, etc.
I agree, situations for when you need to implement a logic system are not extremely common, but maybe I just have not worked in industries where they are - on top of my head I can think of: factory floor scheduling; regulatory compliance (e.g., complex tax rules); insurance systems, risk-calculation (credit approval); strategy games; retail - complex discounting; etc.
Same reason you’d reach for SQL when querying relations - a good enough tool designed for the job.
The problem has always been getting facts into the prolog system. I’ve been looking for a prolog which is as easy to embed in eg Python or node as a Postgres client and… crickets.
I'm working on a problem that I think logic programming might be a fit for. And I already have a lisp. Anyone interested in giving me some feedback on a mini language for heuristics?
This is very nice, I played with it before and working on a similar idea in CL (I am one of those people who finds the uniformity of no syntax soothing).
Your comment could have been simplified to: "I don't like the syntax"
And that could be optimized further by leaving no comment.
All syntax is learned. None of it is "intuitive". Anything unfamiliar to you will seem unpleasant. Some syntaxes can be better than others, but to make that distinction you'd have to at least cite reasons why one syntax is better than another.
I've taken the liberty of fixing the formatting in your comment so the code reads like code. For HN formatting info, see https://news.ycombinator.com/formatdoc.
But can you please make your substantive points more thoughtfully, without name-calling or shallow dismissals? These things are in the site guidelines: https://news.ycombinator.com/newsguidelines.html.
Very cool! I just cloned the repository, will play with it later.
BTW, Clojure was such a brilliant name (from Rich): Whenever I see a project starting with "Clo" I pay attention.
EDIT: had a chance to try it: a very cool resource!
> Whenever I see a project starting with "Clo" I pay attention.
You're going to love my "Cobol in Clojure" project "Clobol" then!
> Clojure was such a brilliant name
IIRC Rich wanted a name that has CLR and J in it - Clojure initially was officially to be supported on both .Net and Java stacks. Later he realized that keeping it completely compatible on both platforms is an uphill battle. CLR Clojure still exists, but it's not "an officially supported" runtime.
really happy to see something of a revival of interest for logic programming lately. it's an extremely powerful tool if you know when to reach for it.
When would you reach for it?
Scheduling, e.g., course scheduling - allocating rooms, professors, time slots while satisfying constraints; Product configuration systems - helping customers select compatible options for complex products; Genealogical research - querying family relationships and ancestry; Static analysis tools for code - finding bugs or verifying properties without execution; Medical diagnosis systems - inferring conditions from symptoms based on medical knowledge; Travel planning - finding optimal routes with multiple constraints; Legal reasoning systems - determining applicability of laws to specific cases; Natural language interfaces - parsing questions and generating appropriate database queries; Hardware verification - proving correctness of circuit designs; Puzzle solvers - Sudoku, crosswords, logic puzzles;
Basically anything that excels when declarative specification of relationships is more natural than imperative algorithms.
This all makes perfect sense. The gap I usually have - and I admit its probably something of a skill issue, I have relatively little formal CS background - is how these abstract declarations of rules are integrated into a product. The example code in projects like this is usually pretty dense and intangible.
Does anyone have good examples of open source codebases or reading material in this area? Lets imagine I have a set of complex business rules about the way a product can be configured and I want to use a logic programming language to enforce them, called from a web interface based on config data stored in a traditional relational database. Is that... a misunderstanding of how these things are to be used?
I've love a good book about how to bring tools and techniques for logical correctness into a Rails ecosystem... or similar language/framework for app dev. I love the promises many of logic languages make but can't rewrite existing applications in them wholesale and it seems like they're a poor fit for that anyways. How are people blending these worlds at large enterprises? Maybe the answer is that nobody really is yet, and thats what makes things like Clolog + Clojure so exciting?
FWIW I have no formal CS background whatsoever (maybe you shouldn't even listen to me on this matter), but if you want to gain some understanding of rule engines, you probably shouldn't start with core.logic or clolog (I have not looked into this project myself just yet, so my assumptions might be completely misleading) - core.logic imo good for complex constrains and relationships, it's based on miniKanren, but has quite steep learning curve, and not sure if it's worth the effort (as a starting point).
oakes/odoyle-rules is a forward-chaining rules engine with a more straightforward approach - for someone already familiar with Clojure, it should be fun to try out. Then maybe check out Clara Rules, if I'm not mistaken the lib is specifically designed for business rules processing. For understanding the theoretical pieces, you probably want to look into forward vs. backward chaining rule systems; pattern matching used in rules engines; understanding how to model domain rules declaratively; Rete algorithm (odoyle lib explains it and iirc links to the paper).
Great comments, thank you for taking the time to mentor a few interested strangers.
Awww, thank you. As a Clojurian, I aspire to be kind and helpful. The Clojure community is renowned for its friendly, coaching-oriented attitude. Anyone with questions (even those unrelated to Clojure) should absolutely reach out to Clojuristas — just go to http://clojurians.net and don't be shy.
I'm forever thankful for Clojure for reigniting my passion for programming, but particularly, I'm indebted to the many individuals in the Clojure community. Whenever I pose a question expecting just straightforward guidance or documentation links, I consistently receive profound, thought-provoking answers that surpass my expectations. Virtually every discussion I initiate with them ends up being incredibly educational, teaching me far more than I initially sought. I can confidently admit - yes, learning Clojure has made a better programmer out of me, but most importantly, it made me a better person.
Well the bigger question is how big does the system have to be to warrant breaking out a new technique, much less adding a new runtime or other large dependency.
Now, I have no direct experience with any of the common logical programming systems. I have familiarity.
But anytime I came upon anything that might justify such a system, the need just didn’t seem to justify it.
Talking less than 100 rules. Most likely less than a couple dozen. Stacking some IFs and a bit of math, strategically grouped in a couple aptly named wrapper methods to help reduce the cognitive load, and it’s all worked pretty well.
And, granted, if I had solid experience using these systems, onboarding cost would be lower.
When have you found it to be worth cutting over?
Absolutely valid and befitting point - adding complexity without clear benefits never should be justified. Most (business) applications have ruleset logic for specific problems not exceeding a dozens of rules - regular code often works fine.
Logic systems tend to show the value when rules become complex with many interdependencies or non-linear execution patterns emerge, or rules change frequently or need to be defined at runtime; when you need explanation tools - e.g., why was this conclusion reached?, etc.
I agree, situations for when you need to implement a logic system are not extremely common, but maybe I just have not worked in industries where they are - on top of my head I can think of: factory floor scheduling; regulatory compliance (e.g., complex tax rules); insurance systems, risk-calculation (credit approval); strategy games; retail - complex discounting; etc.
I've seen shops (e.g. Netflix I think) use Datalog for certain query types.
Same reason you’d reach for SQL when querying relations - a good enough tool designed for the job.
The problem has always been getting facts into the prolog system. I’ve been looking for a prolog which is as easy to embed in eg Python or node as a Postgres client and… crickets.
I dunno which postgres client you're thinking of but:
https://github.com/tau-prolog/tau-prolog
https://pyswip.org/ https://www.swi-prolog.org/packages/mqi/prologmqi.html
Unfortunately the tau site's certificate seems to have lapsed sometime in the last week or so, but I swear it's actually very good.
I'm working on a problem that I think logic programming might be a fit for. And I already have a lisp. Anyone interested in giving me some feedback on a mini language for heuristics?
https://marimo.io/p/@paddy-mullen/notebook-b79pj7
This is very nice, I played with it before and working on a similar idea in CL (I am one of those people who finds the uniformity of no syntax soothing).
I absolutely love the aesthetic of a repo having a giant README.md
I think about docs a lot and the best docs are the ones that are easiest to find. There is few things right in front of you more than README.md
This might unironically be a reason for me to finally try Clojure!
Can anybody comment on when or why to choose this over core.logic?
[flagged]
Your comment could have been simplified to: "I don't like the syntax"
And that could be optimized further by leaving no comment.
All syntax is learned. None of it is "intuitive". Anything unfamiliar to you will seem unpleasant. Some syntaxes can be better than others, but to make that distinction you'd have to at least cite reasons why one syntax is better than another.
I've taken the liberty of fixing the formatting in your comment so the code reads like code. For HN formatting info, see https://news.ycombinator.com/formatdoc.
But can you please make your substantive points more thoughtfully, without name-calling or shallow dismissals? These things are in the site guidelines: https://news.ycombinator.com/newsguidelines.html.
I’ve been programming for 25 years and this looks fine to me. Perhaps it is you who is the problem here and not the code?
[flagged]