Rust 1.29.2

# References and Borrowing

There is a new edition of the book and this is an old link.

> A reference refers to a value but does not own it. Because it does not own it, the value it points to will not be dropped when the reference goes out of scope.

    fn calculate_length(s: &String) -> usize { // s is a reference to a String
        s.len()
    } // Here, s goes out of scope. But because it does not have ownership of what
      // it refers to, nothing happens.Run

Here are the relevant sections in the new and old books:

- In the second edition: Ch 4.02 — References and Borrowing
- In the first edition: Ch 3.9 — References and Borrowing