Iterator Helper Methods

In addition to the next method that defines how an iterator behaves, the Iterator trait provides 70+ helper methods that can be used to build customized iterators.

fn main() {
    let result: i32 = (1..=10) // Create a range from 1 to 10
        .filter(|x| x % 2 == 0) // Keep only even numbers
        .map(|x| x * x) // Square each number
        .sum(); // Sum up all the squared numbers

    println!("The sum of squares of even numbers from 1 to 10 is: {}", result);
}
This slide should take about 5 minutes.

  • The Iterator trait implements many common functional programming operations over collections (e.g. map, filter, reduce, etc). This is the trait where you can find all the documentation about them.

  • Many of these helper methods take the original iterator and produce a new iterator with different behavior. These are know as “iterator adapter methods”.

  • Some methods, like sum and count, consume the iterator and pull all of the elements out of it.

  • These methods are designed to be chained together so that it’s easy to build a custom iterator that does exactly what you need.

More to Explore

  • Rust’s iterators are extremely efficient and highly optimizable. Even complex iterators made by combining many adapter methods will still result in code as efficient as equivalent imperative implementations.