Rust 1.29.2

# Choosing your Guarantees

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

> Smart pointers are data structures that act like a pointer, but they also have additional metadata and capabilities. The different smart pointers defined in Rust’s standard library provide extra functionality beyond what references provide.

    let b = Box::new(5);
    println!("b = {}", b);Run

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

- In the second edition: Ch 15.00 — Smart Pointers
- In the first edition: Ch 4.8 — Choosing your Guarantees