Immutable variables in Rust - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an immutable variable named x with value 5.

Rust

let [1] = 5;

Drag options to blanks, or click blank then click option'

Amut x

Blet mut x

Cvar x

Dx

Attempts:

3 left

💡 Hint

Common Mistakes

Adding mut makes the variable mutable, which is not what we want.

Using var is not valid syntax in Rust.

In Rust, variables are immutable by default. To declare an immutable variable named x, just write let x = 5;.

2fill in blank

medium

Complete the code to print the value of the immutable variable y.

Rust

let y = 10;
println!("[1]", y);

Drag options to blanks, or click blank then click option'

A"{}"

B"value"

C"y"

D"%d"

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around the variable name inside the string prints the name, not the value.

Using %d is not valid in Rust's println! macro.

To print a variable's value in Rust, use println!("{}", variable);. The curly braces {} are placeholders for the variable.

3fill in blank

hard

Fix the error in the code by completing the blank to make the variable z immutable.

Rust

let [1] = 20;
z = 30; // This line causes an error

Drag options to blanks, or click blank then click option'

Amut z

Bz

Clet z

Dvar z

Attempts:

3 left

💡 Hint

Common Mistakes

Adding mut to fix the error changes the variable to mutable, which is not the goal.

Using var is invalid syntax in Rust.

The variable z is declared immutable by let z = 20;. Trying to assign a new value to z causes an error because immutable variables cannot be changed.

4fill in blank

hard

Fill both blanks to declare an immutable variable a with value 15 and print it.

Rust

let [1] = 15;
println!("[2]", a);

Drag options to blanks, or click blank then click option'

Aa

B"{}"

C"a"

Dmut a

Attempts:

3 left

💡 Hint

Common Mistakes

Using mut a makes the variable mutable, which is not needed.

Printing "a" prints the letter 'a', not the variable's value.

Declare a as immutable with let a = 15;. To print its value, use println!("{}", a);.

5fill in blank

hard

Fill all three blanks to declare an immutable variable name with value "Rust", then print it with a message.

Rust

let [1] = [2];
println!("Hello, [3]!");

Drag options to blanks, or click blank then click option'

Aname

B"Rust"

C{}

Dmut name

Attempts:

3 left

💡 Hint

Common Mistakes

Using mut name makes the variable mutable.

Forgetting to add the variable as an argument to println! causes errors.

Declare name as immutable with let name = "Rust";. To print it inside a message, use println!("Hello, {}!", name);.