% Lifetimes
There is a new edition of the book and this is an old link.
> Every reference in Rust has a lifetime, which is the scope for which that reference is valid.
> Most of the time lifetimes are implicit and inferred.
```rust
{
let x = 5; // -----+-- 'b
// |
let r = &x; // --+--+-- 'a
// | |
println!("r: {}", r); // | |
// --+ |
} // -----+
```
---
Here are the relevant sections in the new and old books:
* **[in the current edition: Ch 10.03 — Lifetimes][2]**
* [In the first edition: Ch 3.10 — Lifetimes][1]
[1]: https://doc.rust-lang.org/1.30.0/book/first-edition/lifetimes.html
[2]: ch10-03-lifetime-syntax.html