Rust Loops

A loop is a control structure that enables the repetitive execution of a block of code. Loops are employed for tasks that require multiple iterations, such as iterating through a list of items, performing calculations, or waiting for a specific condition to be met. In Rust there are three main types: for, while and the infinite loop.

Syntax

For loop

The for loop is used to iterate over collections or ranges. It automatically iterates through elements and executes a code block for each item in the pool or scope. It’s commonly used for iterating over arrays, vectors, and other iterable data structures.

let numbers = ["A", 2,20, 4, 5];
for num in numbers.iter() {
    // Code to be executed for each element in the array
    println!("Number: {}", num);
}

While Loop

The while loop repeatedly executes a block of code as long as a specified condition remains true. It checks the condition before entering the loop, and if the condition is initially false, the loop won’t run. While loops are useful when the number of iterations is not known in advance.

let mut counter = 0;
while counter < 5 {
    // Code to be executed while the condition is true
    counter += 1;
}

Infinite Loop

The loop keyword creates an infinite loop that continues executing the code block indefinitely until it’s explicitly interrupted with a break statement. It’s useful when a task must be performed until a certain condition is met within the loop.

fn main() {
    loop {
        println!("Enter 'exit' to quit: ");
        let mut input = String::new();
        std::io::stdin().read_line(&mut input).expect("Failed to read line");

        if input.trim() == "exit" {
            break;
        }
    }
}

Examples

The first example demonstrates a while loop that iterates through each integer from 5 to 10. The second example uses a for loop to iterate over an array that contains the integers in the range 1 to 5.

fn main() {
    let mut counter = 5;
    while counter <= 10 {
        println!("This is iteration number: {}", counter);
        counter += 1;
    }

    let numbers = [1, 2, 3, 4, 5];

    for number in numbers.iter() {
        println!("Number: {}", number);
    }
}

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This example results in the following output:

This is iteration number: 5
This is iteration number: 6
This is iteration number: 7
This is iteration number: 8
This is iteration number: 9
This is iteration number: 10
Number: 1
Number: 2
Number: 3
Number: 4
Number: 5

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