alt Hacker NewsIn short, "Here are my gripes about Prolog, a language that I don't understand."
It's perfectly fine to not like Prolog, but I do feel that if you're going to write an article about why you don't like it, you should at least spend some time figuring it out first.
He says of the cut operator "This is necessary for optimization but can lead to invalid programs." Imagine if a programmer new to C++ said the same thing of the "break" keyword. That's how ridiculous it sounds. Yes, cut can be used to prune backtracking and eliminate unneeded work, but that's hardly it's purpose. It leads to "invalid" programs (by which I assume he means, programs that do something other than what he wants) only in cases where you are using it wrong. Cut is no more "necessary for optimization" than break is. It's a control structure that you don't understand
Negation (\+) is confusing, and the author correctly provides examples where its meaning is unintuitive when applied to unbound variables. That's because it's not strictly speaking a negation predicate, but rather a "not provable" predicate. In that light, the examples in the article make perfect sense. Yes, Prolog is a programming language, so the order of terms matter, even if the order wouldn't matter in pure logic.
Look, Prolog is a weird language. It has a learning curve. It's not "just another language" in the Java, C++, Pascal, Python mold. I get it. But this article has the flavor of an impatient newbie getting frustrated because he can't be bothered to read the documentation.
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I thought the same thing.
I, too, am a big fan of prolog and have (at least) yearly binges where I write a lot of it for fun and profit (and some frustration), but I do not consider myself to be an expert. But even I can see that the author has what I would consider a pretty basic understanding of prolog. Which makes it even more surprising they are writing a book that uses prolog.
Yeah, exactly why I'm not writing the same sort of article about Haskell or prolog. I'm inexperienced in both and the effort to learn them was more than I wanted to spend.
I'm wildly out of my depth here, but sometimes I find I learn quickly if I try out my intuition publicly and fail spectacularly :)
> "This is necessary for optimization but can lead to invalid programs."
Is this not the case? It feels right in my head, but I assume I'm missing something.
My understanding: - Backtracking gets used to find other possible solutions - Cut stops backtracking early which means you might miss valid solutions - Cut is often useful to prune search branches you know are a waste of time but Prolog doesn't - But if you're wrong you might cut a branch with solutions you would have wanted and if Prolog iterates all other solutions then I guess you could say it's provided an invalid solution/program?
Again, please be gentle. This sounded reasonable to me and I'm trying to understand why it wouldn't be. It's totally possible that it feels reasonable because it might be a common misconception I've seen other places. My understanding of how Prolog actually works under-the-hood is very patchy.
> In short, "Here are my gripes about Prolog, a language that I don't understand."
> this article has the flavor of an impatient newbie getting frustrated because he can't be bothered to read the documentation.
The author has written about Prolog in a positive light before (and linked to it in the post), I don't get the impression that these are all "the author doesn't understand what they're doing".
Their first complaint, that "strings are not standardised, so code working with strings in SWI-Prolog is not compatible with Scryer Prolog", seems an appropriate thing to be unhappy about (unless the author is just wrong?).
Your response to their gripe about \+ being "not provable" instead of "negation" notes it's a subtle difference, and that Prolog differs from pure logic there.
The author even notes that doing due diligence, they found a solution to a complaint they had. This doesn't strike me as "can't be bothered to read the documentation".