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Rust 1.31.0

Casting between types

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

A type cast expression is denoted with the binary operator as. Executing an as expression casts the value on the left-hand side to the type on the right-hand side.

fn average(values: &[f64]) -> f64 {
    let sum: f64 = sum(values);
    let size: f64 = len(values) as f64;
    sum / size

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