Comment by z5h
6 hours ago
So first, let's keep in mind that with no execution model, Prolog is still a "syntax" for Horn clauses. It's still a way to document knowledge. Add SLD resolution and we can compute. The paper (intentionally I presume) orders clauses of a simple predicate to illustrate (cause) a problem in Prolog.
But what I actually find is the more time spent in Prolog, the more natural it is to express things in a way that is clear, logical and performant. As with any language/paradigm, there are a few gotchas to be experienced. But generally speaking, SLD resolution has never once been an obstacle (in the past 2 years) of coding.
The general execution model of Prolog is pretty simple. The lack of functions actually makes meta-programming much clearer and simpler. A term is just data, unless it's stated as a goal. It's only a valid goal if you've already defined its meaning.
So I'd be concerned that Curry gives up the simplicity of Prolog's execution model, and ease of meta-programming. I struggle with the lack of types in Prolog, but also know I can (at least in theory) use Prolog to solve correctness problems in Prolog code.
I'm currently using SWI-Prolog. Performance is excellent, it has excellent high-level concurrency primitives[0] (when was the last time you pegged all your cores solving a problem?), and many libraries. I might be one of the few people who has committed to using the integrated editor (PceEmacs) despite being a Vim person. PceEmacs is just too good at syntax highlighting and error detection.
At the same time, I'm a huge fan of Markus Triska. His Youtube[1] stuff is mind-expanding (watch all of it, even if you never write Prolog). He has an excellent book online[2]. I admire the way he explains and advances pure monotonic Prolog, and I appreciate the push for ISO conformance and his support for Prologs that that do the same (SWI is not on that list).
If you want to learn Prolog, watch all of Markus Triska's videos, read his book, and learn what Prolog could be in a perfect world. Then download SWI-Prolog, and maybe break some rules while getting things done at a blazing speed. Eventually you'll gravitate to what makes sense for you.
The Art of Prolog is a classic "must have". Clause and Effect is a good "hit the ground running" (on page 70 you're into symbolic differentiation via term rewriting).
0 https://www.swi-prolog.org/pldoc/man?section=thread
> The Art of Prolog is a classic "must have".
I figured it would be a good introduction to prolog, but to date there doesn't seem to be any prolog interpreter that lets me copy the things in the book to play with them?
I'm currently using SWI-Prolog.
Still checking every now and then if SICStus has open sourced. I used Prolog daily during my PhD and SICStus had such nice features. E.g. it could raise an exception when no more heap space can be allocated or when a 'call' would not finish within a given time. These features made it much easier to use Prolog in real-world systems (this was a parsing system and when parsing a very large corpus, this was highly preferable over simply crashing the interpreter).
Maybe things have changed, but this wasn't possible with SWI at the time. Even worse, most C extensions would use malloc directly, making it impossible to track allocations done by extensions.