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Comment by pirocks | Hacker News Reader

IMO the issue here is with the question mark operator. If the Rust question mark operator was more like Kotlin's this wouldn't be an issue.

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It looks like Kotlin uses ? for nullable types, which isn’t really anything to do with Rust’s ? for short-cut error handling. https://kotlinlang.org/docs/reference/keyword-reference.html

You can also use ? with Option:

  fn process_item(input: Option<Item>) -> Option<Item> {
      let item = input?;
      Some(item + 3)
  }

I'm guessing they're referring the `?.` "safe calls" operator[0-] which essentially acts as a mix of `map` and `andThen` except only for property accesses and method calls, and can be combined with `let` for a more general map-like behaviour.

[0] where many conceive of the operation as `?` being a modifying operator to `.`

In kotlin your example would be:

  fun process_item(input: Item?) -> Item? {
      input?.plus(3)
  }

This would have to be modified in rust to apply to both error and option types, as well as working on stuff other than the . operator, but I think it could be made to work. The main difference is that the ?. operator in kotlin works at the expression level, instead of the function level.

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