Short Q&A from #rust, mainly collecting my (Yurume's) answers

20101028.txt

09:25:37 < duncan> i know i am just doing something stupid, but I am getting a confusing error message trying to implement the Iterator trait: http://is.gd/48ZeJk
09:26:12 < duncan> on the same line, I get 2 opposing errors: "error: wrong number of lifetime parameters: expected 0, found 1" "error: wrong number of type arguments: expected 1, found 0"
09:26:24 < duncan> same line, same column
09:26:42 < Yurume> duncan: Iterator accepts a type parameter, not a lifetime parameter.
09:26:55 < Yurume> maybe you want `impl Iterator<uint> for ...`

13:54:50 < derek_c> I want to iterate through a Vec and remove the first element that satisfies a certain condition.  how may I do so?
13:56:16 < Yurume> derek_c: vec.remove(vec.as_slice().iter().position(|&e| ...).unwrap())

14:23:54 < bananasaur> if i don't need custom syntax is there any benefit to a macro over just inlining a function?
14:24:18 < Yurume> then prefer a simple function, it gives an additional type checking.

20101029.txt

14:52:30 < zekesonxx> So if I want to use an enum like an enum, with the values representing u8s, how can I find the enum value given a u8?
14:52:55 < Yurume> rusti: enum A { x = 1, y = 4, z = 9 } z as uint // zekesonxx, did you mean this?
14:53:18 < zekesonxx> lol and no
14:53:40 < zekesonxx> Say I have the number 4
14:53:45 < zekesonxx> I want to resolve that to y
14:56:35 < Yurume> rusti: #[deriving(Show,FromPrimitive)] enum A { X = 1, Y = 4, Z = 9 } fn to_a(x: uint) -> Option<A> { FromPrimitive::from_uint(x) } (to_a(4), to_a(5)) // zekesonxx, how about this?
14:56:37 -rusti:#rust- (Some(Y), None)

20141030.txt

10:03:32 < reem> Yurume: As in I want to have a 1-lookahead parser
10:03:39 < Yurume> use `Peekable`?

10:52:16 < blaenk> if you're writing a library, how do you handle those warnings about unused code, if you only use them in the tests?
10:52:39 < Yurume> #[cfg(test)]

11:56:47 < Guest59> What's the word on the macro notation?  Is it being changed to @ sign?
11:57:24 < Yurume> Guest59: not yet determined.

14:19:46 < earlz_> would it be at all useful to support hmm.. like named tuples? Basically an inline way of declaring a temporary struct (foo: 1u, bar: 2u).foo
14:20:16 < Yurume> earlz_: Rust once had a structural type. it is determined that the nominal type is suitable for many things, it is now gone.

15:26:07 < derek_c> println doesn't print to stdout in a test, does it?
15:28:13 < Yurume> cargo test -- --nocapture
15:28:20 < Yurume> (note the bare `--`)

16:09:31 < iu> Hey everybody! Is there a trait for implicit conversion between two distinct types?
16:09:37 < Yurume> currently no.
16:09:54 < Sharp> Hopefully never…

20141031.txt

02:29:32 < earlz_> rusti: std::rand::random::<f64>()
02:29:33 -rusti:#rust- 0.986209
02:29:40 < earlz_> how does that even work 
02:29:58 < Yurume> earlz_, f64 implements a Rand trait.
02:30:25 < Yurume> std::rand::random is just a convenient wrappar around Rand

10:26:46 < coryforsyth> did the BigUint struct go away between 0.12.0 and nightly? I see it if I search in the 0.12.0 api docs, but not the nightly
10:27:06 < Yurume> coryforsyth: moved to num crate.
10:28:15 < coryforsyth> Yurume: is num crate now something separate that I need to download/install?
10:28:44 <@huon> coryforsyth: https://github.com/rust-lang/num#usage

10:54:07 < mrob> Is there any way to have a generic function on an integer literal, like with C++ non-type templates?
10:55:39 < mrob> Eg. fn multiply(val: int, T int_literal) -> int
10:56:58 < Yurume> integer static parameter is not there yet

20141103.txt

09:53:42 < awelkie> How can I set the type of Float::two_pi() without setting it to a variable?
09:54:29 < Yurume> awelkie, you can't, but you can use a direct expr `{ let twopi: f64 = Float::two_pi(); twopi }`
09:57:16 <@huon> Yurume: awelkie: I think the planned fully-explicit syntax is `<f64 as Float>::two_pi()`
09:57:30 <@huon> but abbreviations will work when unamgbious, e.g. <f64>::two_pi()

10:12:22 < mrob> How do I loop over an iter and get the index of each item?
10:13:30 < Yurume> mrob: enumerate.

10:15:37 < kurtis> so I was thinking about making an FTP client in Rust for fun. has anyone worked on something like that yet? I don't wanna repeat work.
10:16:14 < Yurume> kurtis: http://www.rust-ci.org/projects/ lists none

10:28:53 < MisterE> If I have struct S { x: [int, ..10000] } and fn new() -> S { ... }, can I know for sure if it's going to copy the whole struct when I call new?
10:30:01 < MisterE> (as in I'd like to avoid large copies)
10:32:06 < Yurume> MisterE: `fn new() -> S { let s = S { x: [0, ..10000] }; s }` won't copy, but you'd better not relying on that.

10:44:10 < kurtis> also, what's the <'a> thing I keep seeing? Can I read up on that somewere?
10:44:26 < Yurume> kurtis: sure, http://doc.rust-lang.org/guide-lifetimes.html

11:30:58 < petervaro> Hi! I need to write from a String from a given index to a to a File. I use the write_str() method for that, but how can I get a substring from my String object (from index to its end)?
11:31:35 < Yurume> petervaro: slice.
11:32:08 < Yurume> rusti: "foobarfoobar".to_string().slice(3, 9).to_string()
11:32:10 -rusti:#rust- barfoo

14:22:50 < ttttt> I'm sure this is a stupid question, but is there a simple way to generate a [u8, ..4] from a Vec<u8>?
14:23:35 < Yurume> ttttt: [v[0], v[1], v[2], v[3]]
14:23:41 < Yurume> sorry about that. :S
14:25:13 < ttttt> I'm storing mp3 frame headers and I thought it would be nice to represent the frame ID that way
14:26:00 < ttttt> I guess "id3v2.3 frame headers"
14:26:25 < Yurume> ttttt: how about read_be_u32() or similar.
14:27:35 < ttttt> Yurume: I could, but the docs for id3v2 are all given in terms of the ascii representation of the frame IDs
14:28:01 < Yurume> ttttt: also try https://github.com/rust-lang/fourcc
14:28:31 < Yurume> ttttt: so that you can use fourcc!("TIT1") instead of 0x54495431

17:04:02 < iu> Hello. What is the standard approach for searching files in a directory by a pattern in Rust?
17:08:07 < Yurume> iu: sorry, that was `std::io::fs::readdir`

17:13:15 < ebfull> is there a way to make my FnMut sized? or some way to approach this? http://is.gd/7UnI69
17:13:50 < Yurume> ebfull: box it. http://is.gd/wDYi0Z