Advent of Rust Day 10 - Persistent iterators

10 Dec 2017

This is a series where I’ll be discussing interesting Rust tidbits that I encounter when solving Advent of Code 2017.

You can find the complete (spoiler) solution here: udoprog/rust-advent-of-code-2017

I’ve realized that a powerful alternative to doing (often unsafe!) arithmetics and indexing is to make use of iterators.

One pattern I’ve found myself moving to is reusing a mutable iterator, like this:

// store an iterator
let mut skip = 0..;

for i in 1..4 {
    for (n, skip) in (0..i).zip(&mut skip) {
        println!("n = {}, skip = {}", n, skip);
    }
}

Playground Link

This would print:

n = 0, skip = 0
n = 0, skip = 1
n = 1, skip = 2
n = 0, skip = 3
n = 1, skip = 4
n = 2, skip = 5

Notice how the skip iterator is shared across all iterations.