Most algorithms that I use from the C++ stdlib take `container.begin()` and `container.end()`, and use the latter to check for the end condition in the main loop. Given that Rust has the `Iter` trait which allows you to iterate straight through any type that implements it, I do not see the point in having multiple mutable references. I mean, sure, it is useful sometimes, but it also brings in a lot of headaches with it :)