Comparison operators in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the '==' operator do in Swift?

The '==' operator checks if two values are equal. It returns true if they are the same, and false if they are different.

beginner

What is the difference between '==' and '!=' operators?

'==' checks if two values are equal, while '!=' checks if two values are not equal.

beginner

Which operator would you use to check if one number is greater than another?

Use the '>' operator to check if the value on the left is greater than the value on the right.

beginner

What does the '<=' operator mean?

The '<=' operator means 'less than or equal to'. It returns true if the left value is smaller than or equal to the right value.

beginner

How do comparison operators help in decision making in Swift?

Comparison operators return true or false, which helps the program decide which path to take, like choosing between options in an if statement.

What will the expression '5 == 5' return in Swift?

A 5

B true

C false

D Error

'5 == 5' checks if 5 is equal to 5, which is true.

Which operator checks if two values are NOT equal?

A ==

B <

C >=

D !=

'!=' means not equal.

What does '3 < 7' evaluate to?

A true

B false

C 3

D 7

'3 < 7' means 3 is less than 7, which is true.

Which operator means 'greater than or equal to'?

A >=

B !=

C ==

D <=

'>=' means greater than or equal to.

If 'a = 10' and 'b = 20', what does 'a != b' return?

A 10

B false

C true

D 20

'a != b' checks if 10 is not equal to 20, which is true.

Explain how comparison operators work in Swift and give examples of at least three different operators.

Think about how you compare numbers or words in real life.

Describe a simple situation where you would use comparison operators in a Swift program.

Imagine choosing what to do based on a condition.

Practice

1. Which of the following comparison operators checks if two values are equal in Swift?

easy

A. ==

B. !=

C. >

D. <=

Solution

1. Step 1: Understand the equality operator

   The operator == is used to check if two values are equal in Swift.

2. Step 2: Compare with other operators

   != means not equal, > means greater than, and <= means less than or equal to.

3. Final Answer:

   == -> Option A

4. Quick Check:

   Equality operator = == [OK]

Hint: Remember: double equals means equality check [OK]

Common Mistakes:

• Confusing == with = (assignment)
• Using != to check equality
• Mixing > and < with equality

2. Which of the following is the correct syntax to check if variable a is not equal to variable b in Swift?

easy

A. a != b

B. a =! b

C. a !== b

D. a <> b

Solution

1. Step 1: Identify the not equal operator in Swift

   Swift uses != to check if two values are not equal.

2. Step 2: Check syntax correctness

   a != b is correct. a =! b is invalid syntax, !== is for identity comparison in some languages but not for value inequality in Swift, and <> is not a Swift operator.

3. Final Answer:

   a != b -> Option A

4. Quick Check:

   Not equal operator = != [OK]

Hint: Not equal always has ! before = [OK]

Common Mistakes:

• Swapping = and ! in != operator
• Using === instead of !=
• Using <> which is not valid in Swift

3. What will be the output of the following Swift code?

let x = 10
let y = 20
print(x > y)

medium

A. true

B. 10

C. 20

D. false

Solution

1. Step 1: Understand the comparison

   The code compares if x (10) is greater than y (20).

2. Step 2: Evaluate the comparison

   Since 10 is not greater than 20, the expression x > y is false.

3. Final Answer:

   false -> Option D

4. Quick Check:

   10 > 20 = false [OK]

Hint: Compare values carefully, > means strictly greater [OK]

Common Mistakes:

• Assuming 10 > 20 is true
• Confusing > with <
• Printing variable values instead of boolean

4. Identify the error in the following Swift code snippet:

let a = 5
let b = 10
if a = b {
    print("Equal")
} else {
    print("Not Equal")
}

medium

A. Using print instead of println

B. Missing parentheses around condition

C. Using = instead of == in if condition

D. Variables a and b must be var, not let

Solution

1. Step 1: Check the if condition syntax

   The condition uses a = b, which is assignment, not comparison.

2. Step 2: Correct operator for comparison

   To compare values, Swift requires == instead of =.

3. Final Answer:

   Using = instead of == in if condition -> Option C

4. Quick Check:

   Comparison needs ==, not = [OK]

Hint: Use == for comparison, = is assignment [OK]

Common Mistakes:

• Using = instead of == in conditions
• Thinking parentheses are mandatory in Swift if
• Confusing print and println functions

5. You want to check if a number n is between 10 and 20 inclusive in Swift. Which of the following expressions correctly uses comparison operators to do this?

hard

A. n > 10 || n < 20

B. n >= 10 && n <= 20

C. n == 10 && n == 20

D. n != 10 && n != 20

Solution

1. Step 1: Understand the range condition

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

2. Step 2: Analyze each option

   n >= 10 && n <= 20 uses n >= 10 && n <= 20, which correctly checks the inclusive range. n > 10 || n < 20 uses OR which is incorrect for range. n == 10 && n == 20 checks if n equals both 10 and 20 simultaneously, which is impossible. n != 10 && n != 20 checks if n is not 10 and not 20, which does not ensure the range.

3. Final Answer:

   n >= 10 && n <= 20 -> Option B

4. Quick Check:

   Inclusive range uses >= and <= with AND [OK]

Hint: Use && with >= and <= for inclusive range checks [OK]

Common Mistakes:

• Using || instead of && for range
• Checking equality to both ends at once
• Using != which excludes values instead of range