5 ms·

fun read(path: &Path): io.Result[Vec[UInt8] { var file = File.open(path).orReturnErr() var bytes = Vec.new() file.readToEnd(&mut bytes).orRetu

by oxnrtr 5y ago

fun read(path: &Path): io.Result[Vec[UInt8] { var file = File.open(path).orReturnErr() var bytes = Vec.new() file.readToEnd(&mut bytes).orReturnErr() Ok(bytes) } would be good enough for me, tbh.

yakubin 5y ago
> File.open(path).orReturnErr() Method syntax is reserved for functions. There are no method syntax macros. Since a return in a function terminates execution of this function, and not its caller, your example would not work.
- zozbot234 5y ago
  Right, so this should really be .orReturnErr , by analogy with .await . We just overload the dot symbol to mean both "method call" and "weird monadic stuff is happening here".
  - simon_o 5y ago
    Exactly. ! for macros was a mistake anyway, I guess that's why they stopped using it with await.
    - yakubin 5y ago
      It wasn't. Without "!" it isn't obvious that you cannot take a: let a: Result<u8, u8> = /* whatever *; let b = match a { Ok(v) => Ok(foo(v)), e => e, }; and transform it into: let a: Result<u8, u8> = /* whatever *; let b = a.map(foo); if "foo" is a macro. When you substitute "foo!" for all the "foo" above, it is obvious.
      - simon_o 5y ago
        Perhaps macros shouldn't do things that aren't "obvious" then?
        infogulch 5y ago
        As a rule, rust rejects the "simpler" choice that instead lay the burden of correctness at the feet of the user. I'm glad they keep a hard line here.
    - steveklabnik 5y ago
      > I guess that's why they stopped using it with await await cannot be a macro, it has to be built into the language, and so it doesn't have the ! because it's not one.
- simon_o 5y ago
  You realize the syntax has changed more than that?
  - yakubin 5y ago
    Yes, but "->" vs ":", or kinds of brackets are superficial, while method syntax has a specific meaning.
scottlamb 5y ago
These differences are mostly superficial. We all need to decide if we're going to avoid a language because its punctuation choices aren't "good enough" for us or if we're going to choose the best tools for building useful systems. "orReturnErr()" seems quite against the Rust philosophy though — refusing the method call syntax for early return means folks can easily miss something important. Rust uses ? for error handling, ! for macros, and keywords (with no parenthesis) for other control flow. I prefer it that way.

by oxnrtr 5y ago

fun read(path: &Path): io.Result[Vec[UInt8] { var file = File.open(path).orReturnErr() var bytes = Vec.new() file.readToEnd(&mut bytes).orReturnErr() Ok(bytes) } would be good enough for me, tbh.

yakubin 5y ago

> File.open(path).orReturnErr() Method syntax is reserved for functions. There are no method syntax macros. Since a return in a function terminates execution of this function, and not its caller, your example would not work.

zozbot234 5y ago
Right, so this should really be .orReturnErr , by analogy with .await . We just overload the dot symbol to mean both "method call" and "weird monadic stuff is happening here".
- simon_o 5y ago
  Exactly. ! for macros was a mistake anyway, I guess that's why they stopped using it with await.
  - yakubin 5y ago
    It wasn't. Without "!" it isn't obvious that you cannot take a: let a: Result<u8, u8> = /* whatever *; let b = match a { Ok(v) => Ok(foo(v)), e => e, }; and transform it into: let a: Result<u8, u8> = /* whatever *; let b = a.map(foo); if "foo" is a macro. When you substitute "foo!" for all the "foo" above, it is obvious.
    - simon_o 5y ago
      Perhaps macros shouldn't do things that aren't "obvious" then?
      - infogulch 5y ago
        As a rule, rust rejects the "simpler" choice that instead lay the burden of correctness at the feet of the user. I'm glad they keep a hard line here.
  - steveklabnik 5y ago
    > I guess that's why they stopped using it with await await cannot be a macro, it has to be built into the language, and so it doesn't have the ! because it's not one.
simon_o 5y ago
You realize the syntax has changed more than that?
- yakubin 5y ago
  Yes, but "->" vs ":", or kinds of brackets are superficial, while method syntax has a specific meaning.

scottlamb 5y ago

These differences are mostly superficial. We all need to decide if we're going to avoid a language because its punctuation choices aren't "good enough" for us or if we're going to choose the best tools for building useful systems. "orReturnErr()" seems quite against the Rust philosophy though — refusing the method call syntax for early return means folks can easily miss something important. Rust uses ? for error handling, ! for macros, and keywords (with no parenthesis) for other control flow. I prefer it that way.