Rust -y scraps: iterating with a step

30 May 2013

This blog post works with Rust v 0.6, and may change in the future :).

A common need in various algorithms is to iterate with some sort of step. A simple way to do this in Rust is with unit::range_step:

let nums = [1,2,3,4,5,6,7];

for uint::range_step(0, bytes.len() - 1, 2) |i| {
    println(fmt!("%d & %d", nums[i], nums[i+1]));
}

This yields

1 & 2
3 & 4
5 & 6

Of course, this is awkward: I wish I had some code to do something like:

let nums = [1,2,3,4,5,6,7];

for nums.in_groups |i, j| {
  println(fmt!("%d & %d", i, j));
}

But I think this is just out of my abilities. The issue is that the closure needs to take the same number of arguments as the step, and I'm not sure that I have the Rust-fu to make it work yet.

After a discussion in the IRC room, Rust doesn't have the Rust-fu yet either; varargs aren't there, so this style is a no-go for now.


Oh, and since there were no examples of this yet, I added some to the docs.