Most active commenters
  • zemptime(3)
  • dragonwriter(3)

←back to thread

Learn Prolog Now

(lpn.swi-prolog.org)
205 points rramadass | 14 comments | 12 Nov 25 14:54 UTC | HN request time: 0.002s | source | bottom
Show context
zemptime ◴[12 Nov 25 16:19 UTC] No.45902006[source]▶
I've recently started modeling some of my domains/potential code designs in Prolog. I'm not that advanced. I don't really know Prolog that well. But even just using a couple basic prolog patterns to implement a working spec in the 'prolog way' is *unbelievably* useful for shipping really clean code designs to replace hoary old chestnut code. (prolog -> ruby)
replies(1): >>45902088 #
1. ramses0 ◴[12 Nov 25 16:26 UTC] No.45902088[source]▶
I keep wishing for "regex for prolog", ie: being able to (in an arbitrary language) express some functional bits in "prolog-ish", and then be able to ask/query against it.

    let prologBlob = new ProLog()
    prologBlob.add( "a => b" ).add( "b => c" )
    prologBlob.query( "a == c?" ) == True
(not exactly that, but hopefully you get the gist)

There's so much stuff regarding constraints, access control, relationship queries that could be expressed "simply" in prolog and being able to extract out those interior buts for further use in your more traditional programming language would be really helpful! (...at least in my imagination ;-)

replies(7): >>45902466 #>>45902575 #>>45902589 #>>45902735 #>>45903753 #>>45904363 #>>45904569 #
2. zemptime ◴[12 Nov 25 16:53 UTC] No.45902466[source]▶
I've wished for the same kind of 'embed prolog in my ruby' for enumerating all possible cases, all invalid cases, etc in test suites. Interesting to know it's not just me!
replies(2): >>45902555 #>>45902588 #
3. naasking ◴[12 Nov 25 16:59 UTC] No.45902555[source]▶
Maybe try a Ruby Kanren implementation:

https://minikanren.org/

uKanren is conceptually small and simple, here's a Ruby implementation: https://github.com/jsl/ruby_ukanren

4. dflock ◴[12 Nov 25 17:00 UTC] No.45902575[source]▶
There are a bunch of libraries that will do this - here's one example of a python one: https://github.com/yuce/pyswip - and a ruby one: https://github.com/preston/ruby-prolog
replies(1): >>45903738 #
5. dflock ◴[12 Nov 25 17:01 UTC] No.45902588[source]▶
There are a bunch of libraries that will do this - here's one example of a python one: https://github.com/yuce/pyswip - and a ruby one: https://github.com/preston/ruby-prolog
replies(1): >>45902772 #
6. dragonwriter ◴[12 Nov 25 17:01 UTC] No.45902589[source]▶
While usually using native syntax rather than strings, somethign like that exists for most languages of any popularity (and many obscure ones), in the form of miniKanren implementations.

https://minikanren.org/

replies(1): >>45905248 #
7. svieira ◴[12 Nov 25 17:13 UTC] No.45902735[source]▶
You might be interested in Flix:

https://play.flix.dev/?q=PQgECUFMBcFcCcB2BnUBDUBjA9gG15JtAJb...

is an embedded Datalog DB and query in a general-purpose programming language.

More examples on https://flix.dev/

8. zemptime ◴[12 Nov 25 17:15 UTC] No.45902772{3}[source]▶
I did try ruby-prolog. The deeper issue is that its just not prolog. Writing in actual prolog affords a lot of clarity and concision which would be quite noisy in ruby-prolog. To me, the difference was stark enough it wasn't worth any convenience already being in ruby was worth.
9. ramses0 ◴[12 Nov 25 18:20 UTC] No.45903738[source]▶
Thanks for the reference! `pyswip` is the closest I've seen so far:

    pl.consult("some-facts.pl")
    pl.assertz("new(fact)")
    while pl.Query(...).nextSolution():
        print( X.value )
...will definitely keep it in my back pocket!
replies(1): >>45904999 #
10. shawn_w ◴[12 Nov 25 18:21 UTC] No.45903753[source]▶
You can do that in Racket, with the Racklog library¹. There's also Datalog² and MiniKanren and probably some other logic languages available.

[1] https://docs.racket-lang.org/racklog/index.html

[2] https://docs.racket-lang.org/datalog/index.html

11. jll29 ◴[12 Nov 25 18:57 UTC] No.45904363[source]▶
What you mean is not "regex for Prolog" but an embedded PROLOG interpreter, which exists.

Ironically, the most common way I have seen people do this is use an embedded LISP interpreter, in which a small PROLOG is easily implemented.

https://www.metalevel.at/lisprolog/ suggests Lisprolog (Here are some embedded LISPs: ECL, PicoLisp, tulisp)

SWI-Prolog can also be linked against C/C++ code: https://stackoverflow.com/questions/65118493/is-there-any-re... https://sourceforge.net/p/gprolog/code/ci/457f7b447c2b9e90a0...

Racklog is an embedded PROLOG for Racket (Scheme): https://docs.racket-lang.org/racklog/

12. tejtm ◴[12 Nov 25 19:06 UTC] No.45904569[source]▶
You could try picat

[0] https://picat-lang.org/

13. dragonwriter ◴[12 Nov 25 19:28 UTC] No.45904999{3}[source]▶
pyswip is a one-way python-to-SWI-prolog interface; there's also a first-party (maintained as part of SWI-prolog), two-way one called janus-swi.

https://pypi.org/project/janus-swi/

https://www.swi-prolog.org/pldoc/man?section=janus-call-prol...

14. dragonwriter ◴[12 Nov 25 19:41 UTC] No.45905248[source]▶
If you really want something that takes Prolog strings instead (and want the full power of prolog), then there are bindings to prolog interpreters from many languages, and also SWI-Prolog specifically provides a fairly straightforward JSON-based server mode "Machine Query Interface" that should be fairly simple to interface with any language.

https://www.swi-prolog.org/pldoc/man?section=mqi-overview