Fast Rust Builds

Re:Fast Rust Builds by oxnrtr on Sunday September 05, 2021 @05:15PM (#28427876)

    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.

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Re:Fast Rust Builds by yakubin on Sunday September 05, 2021 @06:18PM (#28428329)

> 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.

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Re:Fast Rust Builds by zozbot234 on Sunday September 05, 2021 @07:21PM (#28428714)

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".

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Re:Fast Rust Builds by simon_o on Monday September 06, 2021 @06:48AM (#28432409)

Exactly. ! for macros was a mistake anyway, I guess that's why they stopped using it with await.

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Re:Fast Rust Builds by yakubin on Monday September 06, 2021 @07:28AM (#28432656)

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.

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Re:Fast Rust Builds by simon_o on Monday September 06, 2021 @07:32AM (#28432670)

Perhaps macros shouldn't do things that aren't "obvious" then?

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Re:Fast Rust Builds by infogulch on Monday September 06, 2021 @09:11AM (#28433316)

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.

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Re:Fast Rust Builds by steveklabnik on Monday September 06, 2021 @11:43AM (#28434805)

> 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.

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Re:Fast Rust Builds by simon_o on Monday September 06, 2021 @05:50AM (#28432056)

You realize the syntax has changed more than that?

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Re:Fast Rust Builds by yakubin on Monday September 06, 2021 @07:21AM (#28432604)

Yes, but "->" vs ":", or kinds of brackets are superficial, while method syntax has a specific meaning.

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Re:Fast Rust Builds by scottlamb on Sunday September 05, 2021 @07:15PM (#28428668)

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.

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