Hacker News Reader

Comment by em3rgent0rdr | Hacker News Reader

"Exceptions should be... the exception."

The problem is exceptions have entirely opaque flow control. They're the opposite of a goto statement: a comes-from statement if you will. Flow control could originate literally anywhere down the stack and that makes reasoning about what's happening very difficult. Depending on the language it can also have a super broad and ever-changing surface area.

This is not correct, a “comes-from” statement would still be the same behavior as a goto except it’s defined at the label and there is no “goto” at the departure line.

Exceptions are just “goto whatever catch is in the call stack”.

It’s still completely obvious when you see a throw statement that it can throw, and static analysis can tell you exactly what can be thrown by each function.

And it is still opaque where it goes to the programmer when they see it in code. The fact you can use tools to find where it might land (yeah, no shit, you can do same for goto...) is just a mitigation to the problem.

You’re missing the point of exceptions. When you throw an exception, you’re not supposed to care where it lands. That’s the caller’s responsibility.

“Who will catch this” is supposed to be opaque. It’s like wondering who will call this function.

If you want to goto some specific point in the code, just call it.

It unwinds the call stack until a catch.

It is the same "problem" as not knowing where a return will return to.

No, it is not the same problem. You need to trace every function, and every function calling those functions, and every function calling those functions, all the way to catch.

You can't "just" search for function name, you have to rely on code analysis tools.

Making code more opaque coz you can get thru the mess of it via tooling is terrible direction

Return only ever moves up the stack one level. That makes it really easy to reason about. This can move up the stack an unlimited amount, and the handler has to be prepared to properly deal with the current state, no matter where it comes from.

This is no different than returning an error in go far down. You don’t know how far up it will be passed or handled.

You do. Errors have to be handled or passed up explicitly at each level. Errors are one level at a time, not 'n'.

There's nothing opaque about having an implicit potential return after every line as well as an implicit additional error result value. Think Go, but without the ceremony.

Unchecked exceptions need extra care. I've seen process level exceptions being logged when the underlying cause was a failure to parse an integer. The exception was being caught in an exception handler half a dozen scopes away.

Reply on news.ycombinator.com