4 ms·

I'm unsure what "miss" means here. If you forget to add a ?, it's a compilation error.

millstone 8y ago
When I'm reading code, I may not realize that an expression can return, because it can be hard to spot a ? embedded in the middle of the line: sanitize(getFile(getName())?.contents); Swift requires prefixing the line with try, which makes it easier to notice: try sanitize(getFile(getName()).contents) Both are a big improvement over exceptions which have no indication at the call site.
- eridius 8y ago
  In Swift you can still bury that `try` in the middle of the expression sanitize(try getFile(getName()).contents)
- kibwen 8y ago
  Bit of a correction, I believe that `try` in Swift must precede an expression that can throw, rather than preceding a statement that can throw, so AFAICT the Swift code would have to be written like this: sanitize((try getFile(getName())).contents) This sort of illustrates why Rust moved away from its own prefix `try!` macro to its postfix `?` operator: in a language that encourages chaining methods, `foo()?.bar()?.qux()?` looks better than `try!(try!(try!(foo()).bar()).qux())`.
  - dbaupp 8y ago
    No, `try` can be applied to any expression, and will "try" all throwing calls in subexpressions of that: func f() throws -> Int { return 0 } func nothing(_ x: Int) {} func g() throws { nothing(try f()) try (f() + f()) try nothing(f() * f()) } This includes method chains: struct Foo { init() throws {} func bar() throws -> Foo { return self } func qux() throws -> Foo { return self } } try Foo().bar().qux()
    - kibwen 8y ago
      Cool, thanks, I looked in the official docs but didn't notice any mention of this feature. :)
- eddyb 8y ago
  Not sure how many editors' syntax highlighting do this by default, but at least for me, it really helped to make `?` bold red.
ahartmetz 8y ago
"Code is read much more often than written" ;)
- steveklabnik 8y ago
  I think ? is a perfect example of Stroustrup's Rule: https://thefeedbackloop.xyz/stroustrups-rule-and-layering-over-time/ https://thefeedbackloop.xyz/stroustrups-rule-and-layering-ov... > For new features, people insist on LOUD explicit syntax. > For established features, people want terse notation. I was pretty against ? when it was proposed. I liked try!. I thought ? was hard to read. I thought try! was concise enough. After writing (and reading) lots of code with ?, I'm all in. Heck, ? still isn't extendable for user-defined types, and now I want that! We made ? work in main, and in tests. It's now one of my favorite features of Rust. YMMV.
  - moosingin3space 8y ago
    Rust seems to follow Stroustrup's Rule very well as a community. Might explain why I like it so much.
  - ahartmetz 8y ago
    FWIW I don't disagree with Rust's choice, I was just answering the question of parent. I am reading Blandy and Orendorff's Rust book and violently agree with almost all design choices, as an experienced C++ programmer.
    - steveklabnik 8y ago
      Noted :)
TheCycoONE 8y ago
The gp almost certainly means when reading code, not when writing it. Why did this function return here... I don't see anything. Oh wait, there's a ?. On the other hand error handling can distract from the intention of the code, so in another sense ? makes it easier to read. The author can choose if they prefer ?, try!, or a plain old match or if let / return on the Result.

When I'm reading code, I may not realize that an expression can return, because it can be hard to spot a ? embedded in the middle of the line: sanitize(getFile(getName())?.contents); Swift requires prefixing the line with try, which makes it easier to notice: try sanitize(getFile(getName()).contents) Both are a big improvement over exceptions which have no indication at the call site.

eridius 8y ago
In Swift you can still bury that `try` in the middle of the expression sanitize(try getFile(getName()).contents)
kibwen 8y ago
Bit of a correction, I believe that `try` in Swift must precede an expression that can throw, rather than preceding a statement that can throw, so AFAICT the Swift code would have to be written like this: sanitize((try getFile(getName())).contents) This sort of illustrates why Rust moved away from its own prefix `try!` macro to its postfix `?` operator: in a language that encourages chaining methods, `foo()?.bar()?.qux()?` looks better than `try!(try!(try!(foo()).bar()).qux())`.
- dbaupp 8y ago
  No, `try` can be applied to any expression, and will "try" all throwing calls in subexpressions of that: func f() throws -> Int { return 0 } func nothing(_ x: Int) {} func g() throws { nothing(try f()) try (f() + f()) try nothing(f() * f()) } This includes method chains: struct Foo { init() throws {} func bar() throws -> Foo { return self } func qux() throws -> Foo { return self } } try Foo().bar().qux()
  - kibwen 8y ago
    Cool, thanks, I looked in the official docs but didn't notice any mention of this feature. :)
eddyb 8y ago
Not sure how many editors' syntax highlighting do this by default, but at least for me, it really helped to make `?` bold red.

ahartmetz 8y ago

"Code is read much more often than written" ;)

steveklabnik 8y ago
I think ? is a perfect example of Stroustrup's Rule: https://thefeedbackloop.xyz/stroustrups-rule-and-layering-over-time/ https://thefeedbackloop.xyz/stroustrups-rule-and-layering-ov... > For new features, people insist on LOUD explicit syntax. > For established features, people want terse notation. I was pretty against ? when it was proposed. I liked try!. I thought ? was hard to read. I thought try! was concise enough. After writing (and reading) lots of code with ?, I'm all in. Heck, ? still isn't extendable for user-defined types, and now I want that! We made ? work in main, and in tests. It's now one of my favorite features of Rust. YMMV.
- moosingin3space 8y ago
  Rust seems to follow Stroustrup's Rule very well as a community. Might explain why I like it so much.
- ahartmetz 8y ago
  FWIW I don't disagree with Rust's choice, I was just answering the question of parent. I am reading Blandy and Orendorff's Rust book and violently agree with almost all design choices, as an experienced C++ programmer.
  - steveklabnik 8y ago
    Noted :)

TheCycoONE 8y ago

The gp almost certainly means when reading code, not when writing it. Why did this function return here... I don't see anything. Oh wait, there's a ?. On the other hand error handling can distract from the intention of the code, so in another sense ? makes it easier to read. The author can choose if they prefer ?, try!, or a plain old match or if let / return on the Result.