go VS trealla

Hey, this is mine. Thanks for submitting it. I'll answer some questions.

> Why?

I ported Trealla Prolog to WASM (WASI) and I was looking for something useful to test it against. I found Spin, which can run WASM+CGI, and landed on this. Making this project exposed a number of bugs in my port that have now been fixed, so consumers of more useful projects[1][2] benefit as well. Also, PHP style templates are just fun! There's something valuable to just being able to shove a little bit of code inside some HTML and get it up on the internet.

I started my webdev journey with PHP many many years ago, and it's nice to revisit it from a different perspective. I don't use the real (elephant) PHP anymore, but I've gained a newfound appreciation for how fun its quick & dirty development style is.

I hope this project can serve as an example of how to use Prolog for fun things. It does showcase some of the cooler dynamic aspects of the language, and the PHP parsing code is like 10 lines of DCG.

> Is it a joke?

Yes and no. The name is certainly a joke. I was pondering what 'Prolog on Rails' might be and thought calling it PHP would be funny. This led to the PHP-style templates which were quick to implement and pretty powerful. Despite the humorous presentation, it does actually work.

> Can you use Prolog for web services?

Yes! For example, SWI has a mature HTTP package: https://www.swi-prolog.org/pldoc/doc_for?object=section(%27p.... It's used to power SWISH, an online Prolog code sharing thing: https://swish.swi-prolog.org/

> Next steps?

I would like to support persistence somehow. I think it'd be really cool if you could use Prolog's dynamic database[3] as a persistent store. Spin has components for Postgres and Redis so it shouldn't be too hard to implement, but I lose the WASI compatibility if I do that... which means I can't use the binary from WAPM, etc.

I would also like to experiment with running Trealla on Cloudflare Workers. I have another project, worker-prolog[4], which uses Tau Prolog (a Prolog written in Javascript) on Workers.

On a somewhat related note, I've also been playing around with Cosmopolitan libc[5]. I got Trealla to compile to an APE executable but there's some issues with the embedded Prolog libraries getting garbled, so I need to improve my GDB skills and figure out what's going on there.

Finally, I'd like to say thanks to Andrew Davison (@infradig on GitHub), the author of Trealla Prolog, for letting me add WASM support to his project and helping me with lots of things. For example, PHP led to Andrew implementing improvements for using DCGs to parse Prolog terms, which is now super fast[6]!

[1]: https://github.com/guregu/trealla-js

[2]: https://github.com/trealla-prolog/go

[3]: https://www.swi-prolog.org/pldoc/man?predicate=assertz/1

[4]: https://github.com/guregu/worker-prolog

[5]: https://justine.lol/cosmopolitan/

[6]: https://github.com/trealla-prolog/trealla/issues/53

With trealla-prolog/go on the backend and trealla-js on the frontend, you can share the same validation code.

Other resources for logic programming and Go:

ichiban/prolog - ISO Prolog interpreter in pure Go, getting close to v1: https://github.com/ichiban/prolog

trealla-prolog/go - ISO Prolog interpreter embedded via WASM: https://github.com/trealla-prolog/go

guregu/pengine - library for interfacing with Pengines (SWI-Prolog's RPC protocol): https://github.com/guregu/pengine

biscuit-auth/biscuit-go - Biscuits are a fancy auth token with a little Datalog engine: https://github.com/biscuit-auth/biscuit-go

I'm a big fan of logic programming. We've been seeing a small resurgence of interest in it (for example Yarn using Prolog made some waves) and I have some optimism for its future.

Nice article! I think this is an exciting approach to cross-platform support. I took a similar approach for Trealla Prolog's Go library: https://github.com/trealla-prolog/go

The biggest roadblock at the moment is that Go WASM libraries are not in a very good state, except wazero. My assumption is that wazero will be slower than the cranelift-optimized wasmtime, etc. but I have not seen any benchmarks anywhere.

My impressions of the Go WASM libraries:

wazero: great Go-friendly API, not sure about performance, works on all OS (what the author chose)

wasmer: provides bare-minimum input and output for WASI, fast (it's what I chose for trealla-go). Doesn't work on Windows without significant pain, doesn't static compile the wasmer libraries so distribution is a pain. Seems essentially abandoned as its main contributor left the company.

wasmtime: basically impossible to get input and output in any reasonable way (unable to set stdin or read stdout; it can only inherit the FDs from the host), but might finally get buffers for I/O soon.

wasmedge: haven't investigated this yet, but it seems like it solves many of the problems above, promising

If anyone knows of a benchmark between these, I'd love to see it. I can try to run Trealla's against them if it doesn't take too much work.

It was just made private, I guess. Only the Go WebAssembly project is still public: https://github.com/trealla-prolog/trealla-go

spin_version = "1" authors = ["Matt Butcher "] description = "" name = "hello-prolog" trigger = { type = "http", base = "/" } version = "0.1.0" [[component]] id = "hello-prolog" files = [ { source = "./src", destination = "/" } ] # for outgoing HTTP (see spin:http_fetch/3) allowed_http_hosts = [] # "insecure:allow-all" is a special unsafe value to allow any host # access to key-value stores (see spin:store_* predicates) key_value_stores = ["default"] [component.source] url = "https://github.com/guregu/trealla/releases/download/v0.14.4/libtpl-spin.wasm" digest = "sha256:6adb31903bc55e2b5ef3db1619727596f0b08bb789ff6c42df458d0209228677" [component.trigger] route = "/..."

I think that Prolog will rise again. If you have an hour to kill, check out this video introduction by Markus Triska about what makes Prolog unique: https://www.youtube.com/watch?v=8XUutFBbUrg

Recently I have been working on getting Trealla Prolog to run in WebAssembly. Support is quite good now, with an easy-to-use JS library[1], Go library[2], and is now one of the best-supported languages for the Spin runtime[3]. I think it's particularly nice for validations, you can write some simple Prolog rules and run the same code on the client and the server now. I would like to explore this more with a dedicated library at some point. Built-in features like DCGs make parsing/generating all kinds of data trivial. I love it.

I think the biggest barrier to Prolog adoption is that it has a really steep learning curve, and most people get burnt by half-assed introductions in college that tick the 'talked about logic programming' box in the syllabus. You really have to think in a completely different way to write a good Prolog program. But, once you get the right mindset, it makes solving complex problems incredibly easy.

I don't really buy the argument that Datalog is enough. Most Datalog implementations I've seen hack on a bunch of extensions to do things like list membership. It would be awesome to see some serious effort put into an efficient Prolog-based database. The closest thing I can think of is TerminusDB, which I've never used but I wish I could convince my company to try it out ;).

My dream is to have some kind of magical serverless persistent Prolog interpreter in the cloud. That's where I hope to take this Wasm stuff at some point. Can you imagine how powerful it would be to use Prolog instead of GraphQL or whatever? Prolog is IMO the perfect language for querying things, with a 1:1 correspondence to how you write the data. It's like SQL without all the ugly bits (I like SQL too, of course). If this sounds cool to you, check out the paper/book on Web Prolog[4] which is a fascinating dive into what a Prolog-based networked query system could look like.

[1]: http://github.com/guregu/trealla-js

[2]: http://github.com/trealla-prolog/go

[3]: https://github.com/guregu/trealla#spin-components

[4]: https://github.com/Web-Prolog/swi-web-prolog/raw/master/book...

Honestly I can't really say (I just ported it to WASM :-)), but here's more or less the start of the query loop: https://github.com/guregu/trealla/blob/main/src/query.c#L173...

I believe it's a bytecode but I know that function pointers are involved at least with the built-in predicates (see predicates.c).

I think it's a mistake, probably reorganizing things at the moment. You can find a slightly outdated fork here: https://github.com/guregu/trealla