Introduction

The find function in Rust is an iterator adapter that searches for the first element in an iterator that satisfies a given predicate. This function is useful when you need to locate a specific element based on a condition.

Syntax


iterator.find(|&element| condition)

The find function takes a closure that returns a boolean value. It returns an Option containing the first element that satisfies the predicate, or None if no such element is found.

Example Usage

Example 1: Finding the First Even Number

fn main() {
    let numbers = vec![1, 3, 5, 7, 8, 9];
    let first_even = numbers.into_iter().find(|&x| x % 2 == 0);
    println!("{:?}", first_even); // Output: Some(8)
}

Example 2: Finding a Specific String

fn main() {
    let words = vec!["apple", "banana", "cherry"];
    let find_banana = words.into_iter().find(|&word| word == "banana");
    println!("{:?}", find_banana); // Output: Some("banana")
}

Example 3: Finding the First Negative Number

fn main() {
    let numbers = vec![10, 20, -30, 40];
    let first_negative = numbers.into_iter().find(|&x| x < 0);
    println!("{:?}", first_negative); // Output: Some(-30)
}

Example 4: Finding the First Empty String

fn main() {
    let strings = vec!["hello", "world", ""];
    let find_empty = strings.into_iter().find(|&s| s.is_empty());
    println!("{:?}", find_empty); // Output: Some("")
}

Example 5: Finding the First True Value in a Boolean Vector

fn main() {
    let bools = vec![false, false, true, false];
    let first_true = bools.into_iter().find(|&b| b);
    println!("{:?}", first_true); // Output: Some(true)
}

Considerations

The find function short-circuits, meaning it stops processing as soon as it finds an element that satisfies the predicate.
Using find on an empty iterator will always return None.
Ensure the closure used in find does not have side effects, as it may not run for all elements.