Hello! In this lesson, we'll explore the powerful concept of loop control flow in Rust. Control flow in loops allows you to manage the execution of code more effectively within your while and for loops. . Specifically, we'll delve into using conditionals inside loops, the loop construct, controlling loops with break and continue statements, and understanding their significance.

Control flow mechanisms are essential for building complex and functional logic in your programs. By the end of this lesson, you'll be proficient in using these tools to write more efficient and readable code.

Let's get started!

Let's first explore how to incorporate conditionals inside loops. This will help you perform specific actions based on dynamic conditions evaluated during each iteration.

Rust
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1fn main() {
2    let mut num = 0;
3    while num <= 10 {
4        if num % 2 == 0 {
5            println!("{} is even", num);
6        } else {
7            println!("{} is odd", num);
8        }
9        num += 1;
10    }
11}
12/* Output:
13    0 is even
14    1 is odd
15    2 is even
16    3 is odd
17    4 is even
18    5 is odd
19    6 is even
20    7 is odd
21    8 is even
22    9 is odd
23    10 is even
24*/

In this example:

• We initialize num to 0.
• The while loop runs as long as num is less than or equal to 10.
• Inside the loop, we use an if statement to check if num is even or odd, then print the approprita message.
• We increment num by 1.

In Rust, an infinite loop can be created using the loop keyword. To stop the loop, use the break keyword to stop execution of the loop. This is useful when you want to stop a loop once a particular requirement is met. Let's take a look.

Rust
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1fn main() {
2    let mut count = 0;
3    loop {
4        if count == 5 {
5            break;
6            println!("This does not get printed");
7        }
8        println!("Count is: {}", count);
9        count += 1;
10    }
11}
12/* Output:
13    Count is 0
14    Count is 1
15    Count is 2
16    Count is 3
17    Count is 4
18*/

In this example:

• We initialize count to 0.
• The loop runs indefinitely until the break condition is met.
• When count equals 5, the break statement exits the loop.
• The print statement inside the if block does not get executed because the loop stop execution

The continue statement is used to skip the rest of the loop iteration and proceed to the next iteration. This is beneficial when you need to bypass certain actions based on a condition. Let's look at an example where we want to only print odd numbers.

Rust
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1fn main() {
2    for number in 1..10 {
3        if number % 2 == 0 {
4            continue;
5            println!("This does not get printed");
6        }
7        println!("Odd number: {}", number);
8    }
9}
10/* Output:
11    Odd number: 1
12    Odd number: 3
13    Odd number: 5
14    Odd number: 7
15    Odd number: 9
16*/

In this example:

• The for loop iterates over the range 1..10.
• If the number is even, the continue statement skips the rest of the current iteration.
• The print statement inside the if block does not get executed because the loop skips to the next iteration
• If the number is odd, it gets printed.

Combining break and continue with conditionals allows for complex control flow within your loops. Here’s an example of using both together:

Rust
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1fn main() {
2    let mut num = 0;
3    loop {
4        if num > 10 {
5            break;
6            println!("This does not get printed");
7        }
8        if num % 2 != 0 {
9            num += 1;
10            continue;
11            println!("This does not get printed"); 
12        }
13        println!("{} is even", num);
14        num += 1;
15    }
16}
17/* Output:
18    0 is even
19    2 is even
20    4 is even
21    6 is even
22    8 is even
23    10 is even
24*/

In this example:

1. The num variable is initialized to 0.
2. The loop runs indefinitely until the break condition is met.
3. Inside the loop:
   • First, it checks if num is greater than 10 with the condition if num > 10. If this condition is true, the break statement terminates the loop.
   • If not, it checks if num is odd with the condition if num % 2 != 0. If this condition is true:
     • num is incremented by 1.
     • The continue statement skips the rest of the loop iteration, causing the loop to proceed to the next iteration.
     • The println! statement after the continue statement does not get executed, as the continue statement transfers control to the beginning of the loop immediately.
   • If num is even, it reaches the println! statement, which prints the even number message, and then increments num by 1.

Fantastic work! Today, you've delved into the essentials of loop control flow in Rust. You've learned how to use conditionals inside loops, control loop execution with break and continue, and how to combine these tools for complex loop behaviors.

Loop control flow is a powerful technique that allows you to write more efficient and controlled loops. Equipped with this knowledge, it's time to apply what you've learned in practice. Dive into the upcoming exercises to solidify your understanding and explore the true potential of loop control in Rust. Happy coding!