Type inference in Rust - Mini Project: Build & Apply

Type inference

📖 Scenario: You are writing a small Rust program to calculate the total price of items in a shopping cart. Rust can often figure out the type of variables automatically, which is called type inference. This helps you write cleaner code without always specifying types.

🎯 Goal: Build a Rust program that uses type inference to calculate the total price of items in a cart and print the result.

📋 What You'll Learn

Create a variable called prices that holds a list of item prices as floating-point numbers.

Create a variable called total initialized to zero using type inference.

Use a for loop with variables price to iterate over prices and add each price to total.

Print the total price using println!.

💡 Why This Matters

🌍 Real World

Type inference helps programmers write cleaner and shorter code without losing safety. It is used in many Rust programs to reduce clutter.

💼 Career

Understanding type inference is important for Rust developers to write efficient and readable code, which is valuable in software development jobs.

1

Create the list of prices

Create a variable called prices and set it to a list containing these floating-point numbers: 10.5, 20.0, and 5.75.

Rust

# Create a variable called prices with the values 10.5, 20.0, and 5.75
# Your code here

Need a hint?

Use let prices = vec![10.5, 20.0, 5.75]; to create a vector of floats.

2

Create a total variable with type inference

Add a variable called total and set it to 0.0 without specifying its type explicitly.

Rust

fn main() {
    let prices = vec![10.5, 20.0, 5.75];
    // Create a variable called total and set it to 0.0
    // Your code here
}

Need a hint?

Write let total = 0.0; and let Rust figure out the type.

3

Add prices to total using a for loop

Use a for loop with variable price to iterate over prices and add each price to total. Use let mut total to allow changing total.

Rust

fn main() {
    let prices = vec![10.5, 20.0, 5.75];
    let mut total = 0.0;
    // Use a for loop to add each price to total
    // Your code here
}

Need a hint?

Make total mutable with mut and add each price inside the loop.

4

Print the total price

Use println! to print the text Total price: followed by the value of total.

Rust

fn main() {
    let prices = vec![10.5, 20.0, 5.75];
    let mut total = 0.0;
    for price in prices {
        total += price;
    }
    // Print the total price
    // Your code here
}

Need a hint?

Use println!("Total price: {}", total); to show the result.