If expression in Rust - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Rust code using an if expression?

Consider this Rust code snippet. What will it print?

Rust

fn main() {
    let x = 7;
    let y = if x > 5 { "big" } else { "small" };
    println!("{}", y);
}

A big

B small

C true

D 7

💡 Hint

Remember, the if expression returns a value based on the condition.

The variable y is assigned the string "big" because x is 7, which is greater than 5.

🧠 Conceptual

intermediate

What type must both branches of an if expression have in Rust?

In Rust, when using an if expression to assign a value, what must be true about the types of the values in the if and else branches?

A They must be the same type.

B They can be any types, Rust will convert automatically.

C They must both be integers.

D They must both be strings.

💡 Hint

Think about how Rust enforces type safety.

Rust requires both branches of an if expression to have the same type so the compiler knows the type of the whole expression.

❓ Predict Output

advanced

What does this Rust code print?

Analyze the following Rust code and select the output it produces.

Rust

fn main() {
    let a = 10;
    let b = 20;
    let max = if a > b { a } else { b };
    println!("{}", max);
}

A 10

B 20

C a

D b

💡 Hint

The if expression chooses the bigger number.

Since b (20) is greater than a (10), the else branch runs and max is 20.

🔧 Debug

advanced

What error does this Rust code produce?

Look at this Rust code snippet. What error will the compiler show?

Rust

fn main() {
    let x = 5;
    let y = if x > 3 { 10 } else { "small" };
    println!("{}", y);
}

A no error, prints 10

B unused variable warning

C mismatched types error

D missing semicolon error

💡 Hint

Check the types returned by each branch of the if expression.

The if branch returns an integer (10), but the else branch returns a string ("small"). Rust requires both branches to have the same type, so it raises a type mismatch error.

🚀 Application

expert

How many items does this Rust vector contain after running?

Consider this Rust code using an if expression inside a vector initialization. How many elements does the vector v have?

Rust

fn main() {
    let condition = true;
    let v = vec![1, 2, if condition { 3 } else { 4 }];
    println!("{}", v.len());
}

A 2

B 4

C 1

D 3

💡 Hint

Count all elements added to the vector.

The vector v contains three elements: 1, 2, and either 3 or 4 depending on the condition. Since the condition is true, the third element is 3, so the length is 3.