Boolean type in Rust - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a boolean variable named is_active with the value true.

Rust

let is_active: bool = [1];

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

A"true"

BTrue

Ctrue

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase True instead of lowercase true

Using 1 or "true" as boolean values

In Rust, the boolean type is bool and the values are true or false (all lowercase).

2fill in blank

medium

Complete the code to assign the result of a comparison to a boolean variable.

Rust

let is_equal: bool = 5 [1] 3;

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

A==

B!=

C=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using single = instead of == for comparison

Using != which checks for inequality

The == operator checks if two values are equal and returns a boolean.

3fill in blank

hard

Fix the error in the boolean expression to check if x is less than 10.

Rust

let x = 7;
let is_less = x [1] 10;

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

A<=

B<

C=>

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using <= which means less than or equal

Using => which is invalid syntax

The operator < checks if x is less than 10.

4fill in blank

hard

Fill both blanks to create a boolean expression that checks if num is between 1 and 10 (inclusive).

Rust

let num = 5;
let in_range = num [1] 1 && num [2] 10;

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

A>=

B<

C<=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using > instead of >= for the lower bound

Using < instead of <= for the upper bound

The expression checks if num is greater than or equal to 1 and less than or equal to 10.

5fill in blank

hard

Fill all three blanks to create a boolean expression that checks if value is not equal to 0, less than 100, and greater than 50.

Rust

let value = 42;
let valid = value [1] 0 && value [2] 100 && value [3] 50;

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

A!=

B<

C>

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using == instead of != for the first condition

Mixing up < and > operators

The expression checks that value is not zero, less than 100, and greater than 50.

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