docs: moving from int and uint to us for array access in examples

[alfiedotwtf]

As per rust-lang/rfcs#544

[rust-highfive]

r? @alexcrichton

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[alexcrichton]

I think that as an introduction to Rust that this would actually omit as many suffixes as possible (instead of being explicit), would it be possible to just delete all suffixes?

[alfiedotwtf]

I'm conflicted here. I agree that you would want to aim for the intro to be as easy as possible.

So there's two commits here...

With 4172150, although removing suffixes would be easier for a newbie, it's probably better to drum it in from the start that you probably want to be explicit when indexing by using usize. This way, it's habit forming and a plus if they miss the reasoning in later texts.

As for 48a58dd, that was just to silence the compiler warnings when a newbie were to copy-paste the examples and compile them. Having a screen full of warnings on their first attempt to compile some Rust from the official intro may actually scare them off!

I'm happy to remove all suffixes, but I just thought you may want to hear my reasoning :)

[steveklabnik]

In general, as few suffixes as possible.

This way, it's habit forming

Right, but a bad habit. 😄

Which warnings does this make?

[alfiedotwtf]

Right, but a bad habit.

Fair enough :) Although I was under the impression that you didn't want the default (no-suffix, signed) for array indexing so wanted to make usize habit forming. If I'm right, should indexing into an array cause a type check in the compiler and complain when it's not usize?

As for the warnings, one of the examples "let mut numbers = vec![1i, 2i, 3i];" generates 31 lines of warnings. This could definitely scare off a newbie.

/root/tmp/test/src/main.rs:2:26: 2:28 warning: the `i` suffix on integers is deprecated; use `is` or one of the fixed-sized suffixes                                                                                                                                                                                           
/root/tmp/test/src/main.rs:2   let mut numbers = vec![1i, 2i, 3i];
                                                  ^~  
<std macros>:1:1: 9:54 note: in expansion of vec!
/root/tmp/test/src/main.rs:2:21: 2:38 note: expansion site
/root/tmp/test/src/main.rs:2:26: 2:28 help: add #![feature(int_uint)] to the crate attributes to silence this warning
/root/tmp/test/src/main.rs:2   let mut numbers = vec![1i, 2i, 3i];
                                                  ^~  
<std macros>:1:1: 9:54 note: in expansion of vec!
/root/tmp/test/src/main.rs:2:21: 2:38 note: expansion site
/root/tmp/test/src/main.rs:2:30: 2:32 warning: the `i` suffix on integers is deprecated; use `is` or one of the fixed-sized suffixes
/root/tmp/test/src/main.rs:2   let mut numbers = vec![1i, 2i, 3i];
                                                      ^~  
<std macros>:1:1: 9:54 note: in expansion of vec!
/root/tmp/test/src/main.rs:2:21: 2:38 note: expansion site
/root/tmp/test/src/main.rs:2:30: 2:32 help: add #![feature(int_uint)] to the crate attributes to silence this warning
/root/tmp/test/src/main.rs:2   let mut numbers = vec![1i, 2i, 3i];
                                                      ^~  
<std macros>:1:1: 9:54 note: in expansion of vec!
/root/tmp/test/src/main.rs:2:21: 2:38 note: expansion site
/root/tmp/test/src/main.rs:2:34: 2:36 warning: the `i` suffix on integers is deprecated; use `is` or one of the fixed-sized suffixes
/root/tmp/test/src/main.rs:2   let mut numbers = vec![1i, 2i, 3i];
                                                          ^~  
<std macros>:1:1: 9:54 note: in expansion of vec!
/root/tmp/test/src/main.rs:2:21: 2:38 note: expansion site
/root/tmp/test/src/main.rs:2:34: 2:36 help: add #![feature(int_uint)] to the crate attributes to silence this warning
/root/tmp/test/src/main.rs:2   let mut numbers = vec![1i, 2i, 3i];
                                                          ^~  
<std macros>:1:1: 9:54 note: in expansion of vec!
/root/tmp/test/src/main.rs:2:21: 2:38 note: expansion site
/root/tmp/test/src/main.rs:2:7: 2:18 warning: variable does not need to be mutable, #[warn(unused_mut)] on by default
/root/tmp/test/src/main.rs:2   let mut numbers = vec![1i, 2i, 3i];
                               ^~~~~~~~~~~

[steveklabnik]

So this is now out of date. Can you rebase? I think we removed them since. :)

[alfiedotwtf]

That's what I love... Rust moving fast - it's a feature :)

[alexcrichton]

Can the remaining us suffixes be removed? I would expect inference to drive them to already be us as they're used for indexing, but I could be wrong!

[alfiedotwtf]

@alexcrichton this was interesting experiment! I ran the following to check who's assumption was right:

fn main() { 
    let v = [5,6,7];
    for j in 0..3 {
        println!("{}", v[j]);
        println!("{:?}", j);
    }
} 

I was under the assumption that this was going to be 'is' as 'int' used to be the default but now moved to isize. I was completely off here as integers without a suffix instead default to i32! @alexcrichton expected the output to be 'us' because of the type inference, but this actually outputs the following:

5
0u
6
1u
7
2u

I think what's happening here is that println!() is actually wrong because it's spitting out 'u' and not 'us'! I've submitted edde04b to fix this.

Sorry guys, I was completely wrong! This change should be dropped :)

[alexcrichton]

Thanks for the investigation @Alfie!