"Hello World" example in tutorial doesn't compile

[toolness]

It seems the Hello World example in the tutorial doesn't compile.

Pasting the following code into a file called hello.rs:

fn main(args: ~[~str]) {
    io::println(~"hello world from '" + args[0] + ~"'!");
}

and then running rustc hello.rs returns the following:

hello.rs:2:40: 2:46 error: mismatched types: expected `str/&<R0>` but found `~str` (str/&<R0> vs ~-ptr)
hello.rs:2     io::println(~"hello world from '" + args[0] + ~"'!");
                                                   ^~~~~~
hello.rs:2:50: 2:55 error: mismatched types: expected `str/&<R1>` but found `~str` (str/&<R1> vs ~-ptr)
hello.rs:2     io::println(~"hello world from '" + args[0] + ~"'!");
                                                             ^~~~~
hello.rs:1:0: 1:0 error: Wrong type in main function: found `extern fn(~[~str])`, expecting `extern fn(~[str]) -> ()` or `extern fn() -> ()`
hello.rs:1 fn main(args: ~[~str]) {
           ^
error: aborting due to 3 previous errors

I don't know rust, so I'm not sure what's wrong here or whether the fault is on my end. Any help is appreciated!

[nikomatsakis]

I think you are working with an older version of rust (perhaps 0.3.1?), but using the tutorial that targets the most recent version of Rust. The syntax for strings changed in the meantime: in 0.3.1, no ~ was needed. In the current git version, a ~ is needed (if you read further on in the tutorial, it discusses the distinction between ~ values---which cannot be aliased and can be sent between tasks---and @ values, which are local to a specific task but can be aliased freely).

[pcwalton]

Closing.

[toolness]

Ah, thanks @nikomatsakis.

I wonder, then, if it may be useful to definitively mention the version of Rust that should be used in the tutorial? Right now it seems to indicate that version 0.3.x should be used, since the Installation Section uses wget to retrieve the 0.3 tarball and the "badge" at the bottom-right of the documentation window mentions Rust 0.3.1. Should I file a separate issue for that?

[AngryLawyer]

I agree with @toolness - I had a similar issue when starting as it wasn't clear that the tutorial was using the latest from the repo, as opposed to the last packaged release.

[brson]

What would be a good way to indicate that the tutorial refers to an in-development version? We can bump the version to next (0.4), and possibly tag it with something like '0.4-dev'. I'm not sure how feasible it is to change the installation text based on whether the tutorial is for an in-development or released version.

Possibly in the introductory text too we can explicitly say the version number.

[nikomatsakis]

It seems like bumping the version number so that it reflects the next version and not the last one would be helpful.

[brson]

OK. I'll bump the version number today.

[toolness]

Awesome, thanks @brson!

Another slightly more future-proof alternative is to just have a disclaimer at the beginning of the docs that says it's for the tip of the dev branch, so that readers know to use that when in doubt. Presumably the installation docs would wget https://github.com/mozilla/rust/tarball/master instead of a specific versioned tarball.

Anyhow, just another idea though. Thanks for bumping the version number!

[brson]

OK, the version is bumped on incoming. The new docs won't show up until incoming gets promoted to master. Could be a few days. This is all I plan on doing on this matter for now, so if anybody strongly wants some of these other good ideas implemented I suggest opening new issues.