Rust 1.55.0

# Traits

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

> Traits abstract over behavior that types can have in common.

    pub trait Summarizable {
        fn summary(&self) -> String;
    }

Run

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

- in the current edition: Ch 10.02 — Traits
- in the current edition: Ch 19.03 — Advanced Traits
- In the first edition: Ch 3.19 — Traits