If expression in Rust - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an if expression in Rust?

An if expression in Rust lets you run code only when a condition is true. It can also return a value, making it more than just a decision maker.

beginner

How do you write a simple if expression in Rust?

Use if condition { /* code */ }. For example: <br>if x > 5 { println!("x is big"); }

intermediate

Can if expressions return values in Rust?

Yes! You can assign the result of an <code>if</code> expression to a variable. For example: <br><code>let number = if condition { 5 } else { 10 };</code>

intermediate

What happens if you omit the else branch in an if expression used for assignment?

Rust will give an error because the if expression must return a value in all cases when assigned to a variable.

beginner

How do you write multiple conditions with if in Rust?

Use else if for additional conditions. For example: <br>if x > 5 { ... } else if x == 5 { ... } else { ... }

What does an if expression in Rust return when used in an assignment?

A The value from the executed branch

B Always a boolean

C Nothing, it cannot return a value

D The last executed statement in the program

An if expression returns the value from the branch that runs, which can be assigned to a variable.

Which of these is a correct way to write an if expression in Rust?

A if x > 5: { println!("big"); }

B if (x > 5) then { println!("big"); }

C if x > 5 print!("big");

D if x > 5 { println!("big"); }

Rust uses if condition { } syntax without 'then' or colons.

What error occurs if you assign an if expression without an else branch?

A Missing else branch error

B Mismatched types error

C No error, it's allowed

D Syntax error due to missing semicolon

Rust expects all branches to return the same type; missing else means no value for some cases, causing a type mismatch.

How do you check multiple conditions in Rust?

A Use multiple <code>if</code> statements without <code>else</code>

B Use <code>switch</code> statement

C Use <code>else if</code> after <code>if</code>

D Use <code>elif</code> keyword

Rust uses else if to chain multiple conditions.

What type must the values returned by all branches of an if expression have?

A They must all be the same type

B They can be any types

C They must be booleans

D They must be integers

All branches must return the same type so Rust knows what type the if expression returns.

Explain how an if expression works in Rust and how it can be used to assign values.

Think about how you decide between two options and store the result.

Describe what happens if you use an if expression without an else branch when assigning to a variable.

Consider what Rust expects when it needs a value from all paths.