Introduction

The max function in Rust is used to find the maximum value in an iterator. This function is useful when you need to determine the largest element in a collection.

Syntax


iterator.max()

The max function returns an Option containing the maximum element if the iterator is not empty, or None if the iterator is empty.

Example Usage

Example 1: Finding the Maximum in a Vector of Integers

fn main() {
    let numbers = vec![1, 3, 5, 7, 9];
    let max_value = numbers.iter().max();
    println!("{:?}", max_value); // Output: Some(9)
}

Example 2: Finding the Maximum in a Range

fn main() {
    let range = 1..10;
    let max_value = range.max();
    println!("{:?}", max_value); // Output: Some(9)
}

Example 3: Finding the Maximum String in a Vector

fn main() {
    let words = vec!["apple", "banana", "cherry"];
    let max_word = words.iter().max();
    println!("{:?}", max_word); // Output: Some("cherry")
}

Example 4: Finding the Maximum in a Filtered Iterator

fn main() {
    let numbers = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
    let max_even = numbers.iter().filter(|&&x| x % 2 == 0).max();
    println!("{:?}", max_even); // Output: Some(10)
}

Example 5: Finding the Maximum in an Empty Iterator

fn main() {
    let numbers: Vec<i32> = vec![];
    let max_value = numbers.iter().max();
    println!("{:?}", max_value); // Output: None
}

Considerations

The max function requires that the elements in the iterator implement the Ord trait, which means they can be compared.
Using max on an empty iterator will return None.
The max function consumes the iterator, meaning the iterator cannot be used again after calling max.