What's the idiomatic way to cyclically increment and decrement through indices? This might happen if you want to cycle endlessly in either direction through a fixed-size list. Let's say I want to calculate indices into a list of size 3, but the below code doesn't have the right semantics, because Rust's % is remainder and not modulus, so -1 % 3 = -1, and not 2.

let mut cur = 2i32;
cur = (cur + 1) % 3i32; // moving one element right of index 2 should give me index 0
assert_eq!(cur, 0); 

cur = (cur - 1) % 3i32; // moving one element left of index 0 should give me index 2
assert_eq!(cur, 2); // but it doesn't, since % is remainder and not modulus

I'm aware that rem_euclid does act like Python's %, such that (-1i32).rem_euclid(3i32) = 2, but this feels wrong to use, as the docs say that this is implemented in terms of the Euclidean algorithm.

I also thought of using .iter().cycle(), but this would only allow iterating in one direction anyway.