Rust for Loop

The for loop in Rust is used to iterate a range of numbers. The syntax of for loop is:

for variable in lower_bound_number..upper_bound_number {
    // code block
}

Let's take a look at an example,

Example: Rust for Loop

fn main() {
    // usage of for loop
    for i in 1..6 {
        println!("{}", i);
    }
}

Output

1
2
3
4
5

In this example, we print numbers 1 to 5 using the for syntax. If we look at the example closely, we see

for i in 1..6 {
    println!("{}", i);
}

Here,

• for - is the keyword to start any for loop
• i - is known as the loop variable and should be a valid variable name
• in - is the keyword used to iterate over a series of values with for
• 1..6 - is known as an Iterator where 1 is the lower bound and 6 is the upper bound. This yields values from 1 (inclusive) to 6 (exclusive) in steps of one.

Note: The for loop is also known as a for-in loop because of its syntax.

Working of for Loop

Example: Sum of First 10 Natural Numbers using for Loop

fn main() {
    let mut sum = 0;
    
    // for loop to iterate over first 10 natural numbers
    for i in 1..11 {
        sum += i;
    }
    
    println!("Sum: {}", sum);
}

Output

Sum: 55

Here, we loop over the iterator 1..11, which yields values from 1 to 10. A sum variable is created to sum all the values in each iteration. Finally, we print the sum of all the values.

Note: The 1..11 syntax is also known as a range notation or range operator used to create Iterators in Rust.

To learn more about iterators, visit Rust Iterator.

for (i = 0; i < 10; i++) {
    printf("%d\n", i);
}

fn main() {
    // for loop with inclusive range notation
    for i in 1..=5 {
        println!("{}", i);
    }
}

1
2
3
4
5

fn main() {
    let fruits = ["Apple", "Orange", "Banana"];
    
    // for loop to iterate through items in an array
    for fruit in fruits {
        println!("{}", fruit);
    }
}

Apple
Orange
Banana