Difference between revisions of "Rust-Programming-Language/C2/Control-Flow/English"

Learning Objectives

• Control Flow Statement

System Requirements

• Ubuntu Linux OS version 22.04
• Rust 1.80.0
• Visual Studio Code 1.19.0

Prerequisites

• You should be familiar with compiling and running a Rust program.

Code Files

• The following code file is required to practise this tutorial
• This file is provided in the Code Files link of this tutorial page

Conditional Statements

• if
• else if
• else

statements for making decisions based on conditions.

It always returns a boolean value.

We can see a terminal window at the bottom.

> cargo new functions

Type the command cargo new controlflow and press Enter

Open the created project as shown.

let n = 100;

if n>100{

println!("Greater than 100");

}else if n==100{

println!("Equal to 100");

}else {

println!("Smaller than 100");

}

}

If n is greater than 100, it prints a “greater than 100” statement.

If n equals 100, the second print statement will be executed.

If n is less than 100, it prints “smaller than 100”.

You can include multiple else if statements to check multiple conditions in sequence.

The condition must be true to run the code wrapped to it.

Press Ctrl and S to save the file.

Now let us run the program.

The output shows “equal to 100” as we assigned n as 100 in the program.

Loop

• A loop is used to repeat a block of code until the specified condition is met

• The loop keyword creates an infinite loop unless you explicitly break out of it

• Rust provides several ways to loop, including loop, while, and for

Clear the code window and replace the code from the Code file as shown.

let mut count = 0; loop { count += 1; println!("Count: {}", count); if count == 5 { break; } } }

A loop is created in which it increases the count variable by 1.

It prints the value of count in the current iteration.

It will also check for the if statement condition.

When the variable count will be equal to 5, it will stop executing and come out of the loop.

If there is no if statement, it will execute infinitely.

Press Ctrl and S to save the file.

Let us run the program.

We can see the count variable is printed from 1 to 5.

It stops executing when the count reaches 5.

Replace the code from the code file with the while loop program.

let mut counter = 1;

// usage of while loop

while counter < 6 {

println!("{}", counter);

counter += 1;

}

}

Here, the loop keeps running till the counter variable is less than 6.

Inside the loop, we are increasing the value of the counter by 1.

After the 5th iteration, the value of the counter will be 6.

So the condition, counter < 6 becomes false and the loop is terminated.

Save the program.

Check the output.

For loop

• The for loop iterates over a range or a collection
• An iterator which provides a way to access elements one at a time.
• In a For loop, many collections like arrays, vectors, and ranges, implement the Iterator

For loop -example fn main() { for n in 0..11 { println!("{}", n);

}

}

A range with two dots like 0..11 is inclusive on the left.

That is it starts at 0 and exclusive on the right. That is ends at 10

This program will print numbers from 0 to 10.

Clear the code window and copy and paste the code from the Code file.

let data = [2, 1, 17, 99, 34, 56];

for i in data.iter(){

println!("{}", i);

}

}

The data.iter() method creates an iterator for the array data.

The for loop takes each element produced by the iterator and binds it to the variable data.

Inside the for loop, println is used to print the value of each element.

Save the file.

Let us execute the program.

We can see the array elements are printed in the sequence.

Let us see how to use a reverse method in the for loop.

for i in (1..=11).rev() {

println!("{i}...");

} println!("Launch!");

}

If we want the range to include 11 as well, we can write it as (1..=11).

This is known as an inclusive range.

The rev() method is applied to the range to produce a reverse iterator.

This means the number will be fetched in reverse order.

Save the file.

Let us check the output.

We can see the output displayed in the reverse order as expected.

Let us summarize.

Assignment

Write a program to print odd numbers between 11 and 1 using a for loop

• Hint: use Rev() method