Bool type and logical operators in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a Boolean variable set to true.

Swift

let isSunny: Bool = [1]

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

Atrue

BTrue

C1

D"true"

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase True instead of lowercase true

Using numbers like 1 instead of Boolean values

Using strings like "true" instead of Boolean literals

In Swift, Boolean values are lowercase true or false. Using true sets the variable to a Boolean true value.

2fill in blank

medium

Complete the code to check if both conditions are true using a logical AND operator.

Swift

let canGoOutside = isSunny [1] hasFreeTime

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

A||

B==

C&&

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using OR operator (||) instead of AND

Using equality (==) instead of logical operators

Using inequality (!=) instead of logical operators

The logical AND operator in Swift is &&. It returns true only if both sides are true.

3fill in blank

hard

Fix the error in the code by choosing the correct logical NOT operator.

Swift

let isRaining = false
let shouldTakeUmbrella = [1]isRaining

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

A!

Bnot

C~

D!!

Attempts:

3 left

💡 Hint

Common Mistakes

Using ~ which is a bitwise NOT, not logical NOT

Using 'not' which is not valid Swift syntax

Using double exclamation marks (!!) which is invalid

The logical NOT operator in Swift is !. It flips a Boolean value from true to false or vice versa.

4fill in blank

hard

Fill the blank to create a Boolean expression that is true if either it is weekend or you have no homework.

Swift

let canRelax = isWeekend [1] noHomework

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

A!=

B&&

C==

D||

Attempts:

3 left

💡 Hint

Common Mistakes

Using AND (&&) instead of OR

Using equality (==) or inequality (!=) operators incorrectly

The logical OR operator || returns true if at least one condition is true.

5fill in blank

hard

Fill all three blanks to create a Boolean expression that is true if the word's length is greater than 3 and the word is not empty.

Swift

let word = "apple"
let condition = (word.count [1] 3) [2] (word [3] "")

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

A>

B&&

C!=

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using == instead of != to check for non-empty string

Using || instead of && which changes logic

Using < instead of > for length comparison

This code checks if a word's length is greater than 3 and the word is not empty. The operators used are > for comparison, && for logical AND, and != for not equal.

Practice

1. Which of the following is a valid Boolean value in Swift?

easy

A. 0

B. 1

C. yes

D. true

Solution

1. Step 1: Understand Boolean values in Swift

   Swift uses true and false as Boolean values, not numbers or words.

2. Step 2: Identify the valid Boolean value

   Among the options, only true is a valid Boolean value.

3. Final Answer:

   true -> Option D

4. Quick Check:

   Boolean values are true or false [OK]

Hint: Remember: Bool values are only true or false [OK]

Common Mistakes:

• Confusing 1 or 0 as Boolean values
• Using words like 'yes' or 'no' instead of true/false

2. Which of the following is the correct way to write a logical AND operation in Swift?

easy

A. a && b

B. a & b

C. a and b

D. a || b

Solution

1. Step 1: Recall Swift logical AND syntax

   Swift uses && for logical AND, not a single ampersand or words.

2. Step 2: Identify the correct syntax

   a && b uses &&, which is the correct logical AND operator.

3. Final Answer:

   a && b -> Option A

4. Quick Check:

   Logical AND in Swift is && [OK]

Hint: Use double ampersand && for AND in Swift [OK]

Common Mistakes:

• Using single & instead of &&
• Writing 'and' as a word
• Confusing AND with OR operator ||

3. What is the output of the following Swift code?

let a = true
let b = false
print(a || b && !a)

medium

A. Syntax error

B. false

C. true

D. nil

Solution

1. Step 1: Evaluate the NOT operator

   !a means NOT true, which is false.

2. Step 2: Evaluate AND operation

   b && !a is false && false, which is false.

3. Step 3: Evaluate OR operation

   a || (result of AND) is true || false, which is true.

4. Final Answer:

   true -> Option C

5. Quick Check:

   Logical operators follow precedence: NOT, AND, OR [OK]

Hint: Remember operator precedence: ! before && before || [OK]

Common Mistakes:

• Ignoring operator precedence
• Evaluating OR before AND
• Confusing !a as true

4. Identify the error in the following Swift code:

let x = true
let y = false
let result = x & y

medium

A. Missing semicolon at the end of the line

B. Using single & instead of && for logical AND

C. Variables x and y must be integers

D. Using let instead of var for result

Solution

1. Step 1: Check logical AND operator usage

   In Swift, logical AND uses &&, not a single &.

2. Step 2: Identify the syntax error

   Using & causes a compile error because it's a bitwise operator, not logical.

3. Final Answer:

   Using single & instead of && for logical AND -> Option B

4. Quick Check:

   Logical AND requires &&, not & [OK]

Hint: Use && for logical AND, & is bitwise [OK]

Common Mistakes:

• Confusing bitwise & with logical &&
• Thinking semicolons are required in Swift
• Assuming let cannot be used for constants

5. You want to check if a number is between 10 and 20 (inclusive) using Boolean logic in Swift. Which expression correctly uses logical operators to do this?

let number = 15
// Which condition is correct?

hard

A. number >= 10 && number <= 20

B. number > 10 || number < 20

C. number >= 10 || number <= 20

D. number > 10 && number < 20

Solution

1. Step 1: Understand the range condition

   To check if number is between 10 and 20 inclusive, it must be greater or equal to 10 AND less or equal to 20.

2. Step 2: Analyze each option

   number >= 10 && number <= 20 uses && with inclusive comparisons, which is correct. Others use OR or exclusive comparisons, which are incorrect.

3. Final Answer:

   number >= 10 && number <= 20 -> Option A

4. Quick Check:

   Use AND to combine both range checks [OK]

Hint: Use && to combine both conditions for range checks [OK]

Common Mistakes:

• Using || instead of && for range
• Using > or < instead of >= or <=
• Mixing OR and AND incorrectly