Comment by JoelMcCracken
2 days ago
The only languages I know that can do prolog-like-constructs as-a-library are lisps, or at least langs that have reasonable symbol constructs. Usability is way way worse if you can’t talk about variables as first class objects.
I was talking to Bob Harper about this specific issue (context was why macro systems are important to me) and his answer was “you can just write a separate programming language”. Which I get.
But all of this is just to say that doing relational-programming-as-a-library has a ton of issues unless your language supports certain things.
I believe Rust uses datafrog, Datalog as a library to implement some of its next gen solvers for traits and lifetimes. Not a lisp and maybe this still isn’t as elegant as you had in mind? Curious how this library compares for you.
https://github.com/rust-lang/datafrog
If you want to see what it looks like when you actually embed Datalog in your language, have a look at Flix: https://flix.dev/
(Select the "Usinag Datalog..." example in the code sample dropdown)
The Rust code looks completely "procedural"... it's like building a DOM document using `node.addElement(...)` instead of, say, writing HTML. People universally prefer the declarative alternative given the choice.
Haskell can do the same, and does with a lot of little embedded DSLs.
Yea I’ve wanted to try using logict to do some larger logic programming stuff. I’ve done it with list monad but found a lot of speed issues, never quite figured out why it was so slow.
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The experimental "Polonius" borrow checker was first implemented with datafrog, but I believe it's been abandoned in favour of a revised (also "Polonius") datalog-less algorithm.