Boolean type in Rust - Mini Project: Build & Apply

Boolean type

📖 Scenario: Imagine you are creating a simple system to check if a store is open or closed based on a boolean value.

🎯 Goal: You will create a boolean variable to represent the store status, then use it to print if the store is open or closed.

📋 What You'll Learn

Create a boolean variable called is_open with the value true

Create a boolean variable called is_closed with the value false

Use an if statement to check is_open and print "Store is open" if true

Use an else statement to print "Store is closed" if is_open is false

💡 Why This Matters

🌍 Real World

Booleans are used everywhere in programming to represent yes/no, on/off, or true/false states, like checking if a user is logged in or if a device is connected.

💼 Career

Understanding boolean types and conditional statements is essential for any programming job because they control the flow of decisions in software.

1

Create boolean variables

Create a boolean variable called is_open and set it to true.

Rust

# Your code here

Hint

Use let to create a variable and true for the boolean value.

2

Add second boolean variable

Add a boolean variable called is_closed and set it to false below is_open.

Rust

fn main() {
    let is_open: bool = true;
    # Your code here
}

Hint

Use let and false to create the second boolean variable.

3

Use if statement to check store status

Use an if statement to check if is_open is true. Inside the if, write println!("Store is open");. Add an else block that prints "Store is closed".

Rust

fn main() {
    let is_open: bool = true;
    let is_closed: bool = false;
    # Your code here
}

Hint

Use if is_open { ... } else { ... } to decide what to print.

4

Print the store status

Run the program to print the store status based on the is_open boolean variable.

Rust

fn main() {
    let is_open: bool = true;
    let is_closed: bool = false;
    if is_open {
        println!("Store is open");
    } else {
        println!("Store is closed");
    }
    # Your code here
}

Hint

Check the console output to see the message.

Practice

1. What values can a Rust bool type hold?

easy

A. Only true or false

B. Any number

C. Any string

D. Only 0 or 1

Solution

1. Step 1: Understand the bool type in Rust

   The bool type in Rust is designed to hold only two values: true or false.

2. Step 2: Compare with other options

   Other options like numbers or strings are not valid for bool. Rust does not treat 0 or 1 as boolean values directly.

3. Final Answer:

   Only true or false -> Option A

4. Quick Check:

   Rust bool = true or false [OK]

Hint: Remember: bool means true or false only [OK]

Common Mistakes:

• Thinking bool can hold numbers
• Confusing bool with integers 0 or 1
• Assuming bool can hold strings

2. Which of the following is the correct way to declare a boolean variable in Rust?

easy

A. let is_active: bool = true;

B. bool is_active = true;

C. var is_active = true;

D. let is_active = boolean true;

Solution

1. Step 1: Recall Rust variable declaration syntax

   In Rust, variables are declared with let, and the type follows the variable name with a colon, like let var_name: type = value;.

2. Step 2: Check each option

   let is_active: bool = true; uses correct Rust syntax for a boolean variable. Options B and C use syntax from other languages. let is_active = boolean true; is invalid syntax.

3. Final Answer:

   let is_active: bool = true; -> Option A

4. Quick Check:

   Rust bool variable = let name: bool = value; [OK]

Hint: Use 'let var: bool = true;' to declare booleans [OK]

Common Mistakes:

• Using C-style declarations
• Using 'var' keyword (not Rust)
• Writing 'boolean' instead of 'bool'

3. What will be the output of this Rust code?

fn main() {
    let a = true;
    let b = false;
    println!("{}", a && b);
}

medium

A. true

B. 1

C. false

D. Compilation error

Solution

1. Step 1: Understand the boolean AND operator

   The expression a && b returns true only if both a and b are true. Here, a is true and b is false.

2. Step 2: Evaluate the expression

   Since b is false, a && b evaluates to false. The println! macro prints this value.

3. Final Answer:

   false -> Option C

4. Quick Check:

   true AND false = false [OK]

Hint: AND is true only if both are true [OK]

Common Mistakes:

• Assuming true && false is true
• Confusing boolean with integer 1 or 0
• Expecting compilation error

4. Identify the error in this Rust code snippet:

fn main() {
    let flag: bool = True;
    println!("{}", flag);
}

medium

A. Variable name 'flag' is invalid

B. bool type cannot be assigned directly

C. Missing semicolon after println!

D. 'True' should be lowercase 'true'

Solution

1. Step 1: Check boolean literal case sensitivity

   In Rust, boolean literals are lowercase: true and false. Using True causes a compilation error.

2. Step 2: Verify other syntax

   The variable name is valid, semicolon is present after println!, and bool can be assigned directly.

3. Final Answer:

   'True' should be lowercase 'true' -> Option D

4. Quick Check:

   Rust bool literals are lowercase true/false [OK]

Hint: Use lowercase true/false in Rust [OK]

Common Mistakes:

• Writing True or False with uppercase
• Thinking semicolon is missing
• Confusing variable name rules

5. Given a variable score of type i32, which Rust expression correctly sets passed as a boolean indicating if score is 50 or more?

hard

A. let passed: bool = score > 50 || false;

B. let passed: bool = score >= 50;

C. let passed: bool = if score >= 50 { true };

D. let passed: bool = score == true;

Solution

1. Step 1: Understand boolean expressions with comparisons

   The expression score >= 50 returns a boolean true if score is 50 or more, otherwise false.

2. Step 2: Evaluate each option

   let passed: bool = score >= 50; directly assigns the comparison result to passed. let passed: bool = score > 50 || false; is incorrect because score > 50 || false excludes 50 itself. let passed: bool = if score >= 50 { true }; is invalid because the if lacks an else branch and thus doesn't return a value when the condition is false (compilation error). let passed: bool = score == true; compares an integer to a boolean, which is invalid.

3. Final Answer:

   let passed: bool = score >= 50; -> Option B

4. Quick Check:

   Comparison returns bool, assign directly [OK]

Hint: Use comparison directly to get bool result [OK]

Common Mistakes:

• Using if without an else branch for assignment
• Comparing int to bool directly
• Using wrong comparison operators