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

Learning Objectives

• Functions

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 File

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

Functions

• It is a set of statements to perform a specific task
• Functions organize the program into logical blocks of code.

Functions

• Functions make the code reusable.
• It structures your programs and makes them more readable and maintainable.

Function - Example // define a function fn greet() {

println!("Hello, World!");

} fn main() {

//function call greet();

}

• Here, we have created a greet() function that prints "Hello, World!" .
• To invoke the created function, we need to make a function call.
• Notice that we are calling the function from inside main().
• In Rust, main() is also a function known as a built-in function that has a special meaning.

We can see a terminal window at the bottom.

> cargo new functions

Type the command cargo new functions and press Enter

Open the created project as shown.

fn add(a: i32, b: i32) { let sum = a + b; println!("Sum of a and b = {}", sum); } fn main() { // call add function with arguments add(12, 10); }

Here, a and b are function parameters.

i32 is the data type of parameters.

12 and 10 are known as function arguments that are passed to the add function.

That means 12 is assigned to a and 10 is assigned to b.

Save the file.

It prints the sum of a and b as 22.

Replace the code as shown.

   length * breadth }

fn main() { let k = area(5, 6); println!("Area of the rectangle = {k}"); }

Change the program to return length*breadth

The area function takes two parameters, length and breadth, both of type i32.

-> i32 right arrow i32 before the opening curly bracket indicates the function's return type.

It returns an i32 value representing the area of the rectangle.

In the next line, notice the lack of a semicolon after length * breadth.

In Rust, the absence of a semicolon signifies that this line is an expression.

The result value is returned by the function.

Save the file and run the program.

We can see the output as the area of the rectangle is 30.

Now let us add a semicolon at the end of length into Breadth statement.

Save the file.

This time we get an error, remove this semicolon to return this value.

This is because it is being considered as a statement and not as a return value.

You can use either conventions 

• length* breadth without semicolon or
• return length * breadth with semicolon

for returning the value.

Save the file and run the program

We can observe that the area of the rectangle is 30.

Summary

In this tutorial, we learn about

• Functions

Let us summarize.

Assignment

• In the main.rs file
  • Create a function that accepts a number as a parameter
  • Print EVEN if the number is even
  • Else print ODD
• Compile and execute the project.
• Observe the output in the Terminal

Thank You