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> But I also don't know any languages where errors _aren't_ values (look, i know you understand how exceptions work, please bear with me) yes, Exception objec
by uryga 5y ago
> But I also don't know any languages where errors _aren't_ values
(look, i know you understand how exceptions work, please bear with me)
yes, Exception objects are technically values, but you don't return them to the caller; you throw them to the, uh, catcher. basically, you get a special, second way of returning something that bypasses the normal one! but in the EaV approach, errors just are returned like every other thing.
the uniformity of EaV comes in handy when doing generic things like mapping a function over a collection - don't have to worry if something will throw, because it's just a value! and that lets you go to some pretty powerful places w.r.t abstraction: see e.g. haskells `traverse`.
but yeah, EaV needs some syntactic sugar to reach ergonomic par with exceptions, otherwise you get if-err-not-nil soup :P
- kevinmgranger 5y agoRight, so the concept in Go is misnamed. It's not Errors are Values, it's Errors Have Normal Control Flow. Returning errors makes many things more manageable, definitely. But where they really shine, like in the mapping example, isn't possible in Go. Unless I'm mistaken with how go generics work. (By the way, I'm a huge fan of how error handling works in Rust and other related functional languages. Definitely not advocating for the classic way of doing Exceptions).
- uryga 5y ago> But where they really shine, like in the mapping example, isn't possible in Go. oh yeah, definitely! Go's version of EaV with multiple returns is pretty lackluster compared to a proper Result type. afaict it's kind of "the worst of both worlds" -- all of the boilerplate of plumbing errors manually w/ none of the benefits.
- kevinmgranger 5y agoFolks are saying that sum types might eventually come to go after some experimenting with generics. It'll be interesting to see where it goes.
- int_19h 5y agoExceptions can still be treated as syntactic sugar for EaV; it just means that every expression has an implicit unwrap-and-propagate.
- kevinmgranger 5y agoDefinitely. But Go's boilerplate for error handling is an overcorrection from the implicit propogation. As folks have mentioned, Rust's `?` or Swift's `try` strike a nice middle ground.
- uryga 5y agoare there any languages that do this? Rust's `?` is similar but the propagation is explicit
- int_19h 5y agoThat's what I'm saying - any language with exceptions can be treated as if it was all Rust-style Result<T, E>, but with implicit ? after every expression. Well, and E is an open variant (like e.g. extensible variant types in OCaml), unless the language has checked exceptions like Java.