Hacker News new | ask | show | jobs
by hyperhello 56 days ago
But that’s because null is a static type. Zero isn’t a static type. How can I know if a calculation produces zero if I can’t predict the result of it at compile time?
2 comments

Post type check analyzers can work with more than just the type information, you can really do whatever you want at this stage. The normal highly optimized type checker handles the bulk of the checking and the post type check analyzers can work on the residual. You wouldn’t type check a file that doesn’t parse, and you wouldn’t run the analyzers on code that doesn’t type check.

The problem is these checks can be rather slow and people don’t want to wait a long time for their type checking and analyzers to finish. But LLMs can both wait longer and by internalizing the logic can reduce the number of times it will need to trigger them.

Edit: I’ll need to examine this project to know where (or if) they draw the distinction between normal type checking and a post type check analyzer. If they blend the two and throw the whole thing into Z3 it’ll work but it’ll be needlessly slow.

Edit: What I’m calling a post type check anyalizer they’re calling a contract verifier and it’s a distinct stage with ‘check’ (type check) then ‘verify’ (Z3).

I think it's about if there's a possibility of it being zero. Of course there's no way to tell at compile time that a value will definitely be zero.

So, in pseudocode

int div(int a, int b): return a / b;

Would probably be a compile time error, but

int div(int a, int b): return b == 0 ? ERR : (a /b);

Would not, or at least that's what I'd expect.

Or it's just some AI brain fart…

The whole things looks vibe-coded, and vibe-designed.

> Of course there's no way to tell at compile time that a value will definitely be zero.

Yes there is. Dependently typed languages like Idris can inspect terms at the value-level during compile time. Rather, instead of proving that the divisor will be zero, you must instead statically prove that the divisor cannot be zero; otherwise the code will not typecheck.

Okay,

int integer_division(int a, int b) { if (b!=0) return a/b; raise(SIGFPE); }

Great.

No. In this type of language, the typical division function does not check against zero. It has a precondition that requires the caller to ensure that the divisor is not zero. If the data the caller has is completely arbitrary, then yes, the caller must use an if statement or similar. If the caller knows something about its data and can be sure that the divisor is not zero, then it doesn't need to use an if statement. But it might need to convince the proof checker that it knows what it's doing.
You don't appear to understand the difference between runtime and static analysis/compile time, or term-level and type-level.
Great! Explain it to us while I read to my kid!
The ‘let me google that for you’ is set to be replaced with ‘let me ask ChatGPT for you’.
This is a very antagonistic comment. Some people would call it "passive aggressive".

Dude, if you're reading to your kid you're clearly busy doing something else. No matter how simple the concept is, if you don't pay attention you're not going to get it so it's a failure on your part and not a failure on the part of the person patiently trying to explain something to you.

Don't get mad because you're too lazy to even ask the AI. You are first to be replaced in the workforce.

Or maybe it's over your head and you should just stick to reading children's fiction after all. Want some colouring books too?