Rust week of 2016-02-12

I enjoyed reading Two Weeks of Rust, a blog post resulting from building something non-trivial using the language.

In terms of learning, I've always been wondering why one does not need mut when reading values from an iterator via a for loop , but does not when reading them using next:

let it = std::env::args() // iterator over CLI arguments
for value in it {
    do_something(value);
}

// versus

let mut it = std::env::args() // iterator over CLI arguments
do_something(it.next());
do_something(it.next());
...

I think with the for loop, it cannot be used anymore, and that's why it can get away with being immutable. I'm not 100% yet... this feels like a lousy explanation.