Introduction

The any function in Rust is an iterator adapter that checks if any element of an iterator satisfies a given predicate. This function is useful when you need to determine if at least one element in a collection meets certain criteria.

Syntax


iterator.any(|element| condition)

The any function takes a closure that returns a boolean value. It returns true if the closure returns true for any element, and false otherwise.

Example Usage

Example 1: Checking for Any Even Numbers

fn main() {
    let numbers = vec![1, 3, 5, 7, 9];
    let has_even = numbers.into_iter().any(|x| x % 2 == 0);
    println!("{}", has_even); // Output: false
}

Example 2: Checking for a Specific String

fn main() {
    let words = vec!["apple", "banana", "cherry"];
    let contains_banana = words.into_iter().any(|word| word == "banana");
    println!("{}", contains_banana); // Output: true
}

Example 3: Checking for Any Negative Numbers

fn main() {
    let numbers = vec![10, 20, -30, 40];
    let has_negative = numbers.into_iter().any(|x| x < 0);
    println!("{}", has_negative); // Output: true
}

Example 4: Checking for Any Empty Strings

fn main() {
    let strings = vec!["hello", "world", ""];
    let has_empty = strings.into_iter().any(|s| s.is_empty());
    println!("{}", has_empty); // Output: true
}

Example 5: Checking for Any True Values in a Boolean Vector

fn main() {
    let bools = vec![false, false, true, false];
    let has_true = bools.into_iter().any(|b| b);
    println!("{}", has_true); // Output: true
}

Considerations

The any function short-circuits, meaning it stops processing as soon as it finds an element that satisfies the predicate.
Using any on an empty iterator will always return false.
Ensure the closure used in any does not have side effects, as it may not run for all elements.