Expression evaluation in Rust - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an expression in Rust?

An expression in Rust is any piece of code that returns a value. For example, 5 + 3 is an expression that evaluates to 8.

beginner

How does Rust evaluate the expression 2 * (3 + 4)?

Rust first evaluates the expression inside the parentheses (3 + 4), which is 7, then multiplies it by 2, resulting in 14.

intermediate

What is the difference between an expression and a statement in Rust?

An expression returns a value and can be part of a larger expression. A statement performs an action but does not return a value. For example, <code>let x = 5;</code> is a statement, while <code>5 + 3</code> is an expression.

beginner

How does Rust handle boolean expressions like 5 > 3 && 2 < 4?

Rust evaluates each comparison: 5 > 3 is true, 2 < 4 is true, then combines them with && (and), resulting in true.

intermediate

What is the role of the match expression in Rust?

The match expression lets you compare a value against patterns and execute code based on which pattern matches. It always returns a value, making it a powerful expression for decision-making.

What does the Rust expression 3 + 4 * 2 evaluate to?

A 11

B 14

C 10

D 7

Rust follows order of operations: multiplication first (4 * 2 = 8), then addition (3 + 8 = 11).

Which of the following is a statement in Rust?

A <code>let x = 10;</code>

B <code>3 * 4</code>

C <code>5 + 3</code>

D <code>7 - 2</code>

let x = 10; is a statement because it declares a variable and does not return a value.

What is the result of true || false && false in Rust?

A false

B true

C error

D none

Rust evaluates && before ||. So false && false is false, then true || false is true.

Which expression correctly uses match to return a value?

A match num { 1 => 10; _ => 20; };

B match num { 1 => println!("One") };

C let x = match num { 1 => 10, _ => 20 };

D let x = if num == 1 { 10 } else { 20 };

Option C uses match as an expression that returns a value assigned to x.

What type of value does an expression in Rust always produce?

A Only integers

B No value

C Only booleans

D A value or unit type <code>()</code>

Every expression in Rust produces a value. If no meaningful value, it produces the unit type ().

Explain how Rust evaluates the expression 4 + 3 * 2 step-by-step.

Think about which part Rust calculates first.

Describe the difference between an expression and a statement in Rust with examples.

Consider what each piece of code produces or does.