From Node.js to Go

Re:From Node.js to Go by Animats on Saturday January 31, 2015 @12:46AM (#8976019)

"try!" is close to something one might call "cruft". It tests a function for an error value, and if it gets one, it returns from the containing function. "try!()" is written like a function call, but it doesn't work like one - it can execute a return statement. That's outside the normal semantics of the language. This is the only macro in the standard macros with such semantics. Fortunately. This is a capability which needs to be used with extreme restraint. Writing a macro "try_except_finally!(maincode, exceptioncode, cleanupcode)" would probably be a bad idea.

There was at one time a fad for extending C with macros like that. Fortunately for program readability, it didn't last.

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Re:From Node.js to Go by Manishearth on Sunday February 01, 2015 @09:11PM (#8982451)

`throw` in Java's exception handling also prematurely exits a function. So?

While `try!()` is a macro and not a core language feature, most of the macros in the standard library can be treated as such. So a Rust programmer will know that `try!()` can return, just like a Java programmer knows that `throw` returns early.

Besides, macros are syntactically distinguishable in Rust. When you see that exclamation mark, you have to rememeber that it's a macro and might be doing arbitrary compile time things along with arbitrary token tree expansion.

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Re:From Node.js to Go by Jweb_Guru on Saturday January 31, 2015 @01:26PM (#8977497)

Except that in Rust, all macros are syntactically distinguished from non-macros (as well as hygienic, unlike C macros), and try! is extremely common (so the claim that people won't know what it does is questionable). I agree that macros like this should be carefully considered, but I think experience has already shown us that try! is perfectly fine.

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