Add core::repeat(int, fn()) function

[brson]

Sometimes you just want to do something some number of times. There's no real concise way to express that right now.

[pwoolcoc]

Where would be the best place to put this function? An existing file in libcore/? A "repeat.rs" file in libcore? or a more general "iterator.rs" file in libcore?

[brson]

There isn't an existing place that makes sense. I was thinking of just putting it into core.rs, but that does pull it into the global scope. I hate to dump it into something as generic as util.rs because nobody will ever find it.

[pwoolcoc]

making an "iter.rs" or "iterator.rs" might make a bit more sense...though "import core::iter::repeat" might be a little word-y.

[brson]

If you are going to go that route then please have a look at the iterator library nmatsakis is working on and which he intends to merge into core or std: https://github.com/nikomatsakis/rust-iter

Repeat doesn't strictly have anything to do with an iterator type, but it clearly has to do with iteration. Maybe we can get @nikomatsakis's opinion

[nikomatsakis]

I could add it to the iter library, I suppose!

As an alternative, what about allowing block parameters to be named "_", meaning "I really don't use this."

Then you could write:

uint::range(0, 10) {|_|
}

which seems marginally nicer than |_i|. And it preserves the invariant that an iterator is something that ends with a block with a single argument. But I don't really care. I guess repeat(10) {|| ... } reads nicer.

[brson]

I do think being able to write |_| would be nice regardless - it comes up frequently.

[pwoolcoc]

I sent @nikomatsakis a pull request for the repeat function.

[kud1ing]

@nikomatsakis: When do you plan to integrate your "iter" module in libcore? The module "str" has has some duplicate functions doing basically the same thing, differing only in either "returning" a list of strings or an iterator. Having iter::to_list in libcore we could settle on only the iteration-versions.

[nikomatsakis]

I plan to merge it today in some form.null

[kud1ing]

That would be awesome.

[brson]

This is done.