Constants in Rust - Mini Project: Build & Apply

Using Constants in Rust

📖 Scenario: You are creating a simple program to calculate the area of a circle. You want to use a constant value for Pi to keep your code clean and easy to update.

🎯 Goal: Build a Rust program that defines a constant for Pi, uses it to calculate the area of a circle with a given radius, and prints the result.

📋 What You'll Learn

Define a constant named PI with the value 3.14159

Create a variable named radius with the value 5.0

Calculate the area using the formula PI * radius * radius

Print the area with a message

💡 Why This Matters

🌍 Real World

Constants are used in programs to store fixed values like mathematical constants, configuration values, or limits that should not change during the program.

💼 Career

Understanding constants is important for writing clear, maintainable, and bug-free code in any software development job.

1

Define the constant PI

Write a constant named PI with the value 3.14159 using const and type f64.

Rust

# Define the constant PI with value 3.14159
# Your code here

Need a hint?

Use const keyword, specify the type f64, and assign the value 3.14159.

2

Create a variable radius

Create a variable named radius with the value 5.0 and type f64.

Rust

const PI: f64 = 3.14159;

// Create a variable radius with value 5.0
# Your code here

Need a hint?

Use let to create a variable, specify type f64, and assign 5.0.

3

Calculate the area of the circle

Create a variable named area that calculates the area using the formula PI * radius * radius.

Rust

const PI: f64 = 3.14159;

fn main() {
    let radius: f64 = 5.0;

    // Calculate the area of the circle
    # Your code here
}

Need a hint?

Use the formula for the area of a circle: Pi times radius squared.

4

Print the area

Print the message "The area of the circle is: " followed by the value of area using println!.

Rust

const PI: f64 = 3.14159;

fn main() {
    let radius: f64 = 5.0;
    let area = PI * radius * radius;

    // Print the area with a message
    # Your code here
}

Need a hint?

Use println!("The area of the circle is: {}", area); inside fn main().