Comment by flir | Hacker News Reader

Comment by flir | Hacker News Reader

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I see a lot of people say this about exceptions, and I don't have that problem. The exception bubbles up the stack until something catches it. Ok it's a different code path, but it's a very simple one (straight up). So you either catch the exception nearby and do something specific with it, or it bubbles up to a generic "I'm sorry there was a problem please try again later" handler.

Honestly makes me wonder what I'm missing. Maybe it's because I don't deal with state much? Do the problems start to mount up when you get into writing transaction locks, rollbacks etc? But I don't see why you wouldn't have the same problems with Go's mechanism.

Hoping to gain enlightenment here.

[copied from a comment below]: They are just horrific gotos that any library can invoke against your code. They are pretty much never, ever handled correctly. And nearly always, after an exception is “handled”, the application is actually in an unknown state and cannot be reasoned about.

Maybe this is it? I prefer a "fail early and often" approach, and I tend to validate my data before I perform operations on it. I don't want to attempt recovery, I want to spew log messages and quit.

Exceptions are difficult to discuss because different languages implement exceptions differently, each with their own downsides. That said, I don't think anyone has an issue with bubbling. Even sum type proponents love Rust's ? shorthand, because it makes it easier to propagate Results up the stack.

The big issue with exceptions in C#, Python and JS is that they're not included in function signatures, which means you have to look up the list of possible exceptions from documentation or source code. This could be amended with checked exceptions like Java, but it allegedly doesn't mesh well with the type system (I haven't personally written Java to confirm this). And then there's the C++ crowd that slaps noexcept on everything for possible performance gains.

Personally, I like the way Koka does exceptions with algebraic effects and type inference. It makes exceptions explicit in function signatures but I don't have to rewrite all the return types (like in Rust) because type inference takes care of all that. It also meshes beautifully with the type system, and the same effect system also generalizes to async, generators, forking and other stuff. Alas, Koka is but a research language, so I still write C# for a living.

> They are pretty much never, ever handled correctly. And nearly always, after an exception is “handled”, the application is actually in an unknown state and cannot be reasoned about.

I think that’s misdirected but illustrates the emotional reasons why people develop a negative impression of the concept. Usually it means someone had bad experiences with code written in a poor culture of error handling (e.g. certain Java frameworks) and generalized it to “exceptions are bad” rather than recognizing that error handling isn’t trivial and many programmers don’t take it seriously enough, regardless of the paradigm. As a simple example, C and PHP code have had many, many security and correctness issues caused by _not_ having errors interrupt program execution where the users would have been much better off had the program simply halted on the first unhandled error.

If you write complex programs with lots of mutable shared state, yes, it’s hard to reason about error recovery but that’s misattributing the problem to the mechanism which surfaced the error rather than the fact that their program’s architecture makes it hard to rollback or recover.

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