Comparison operators in Swift

Introduction

Comparison operators help us check if things are equal or which one is bigger or smaller. They let the program make decisions.

Checking if a password matches the saved one.

Deciding if a player's score is higher than the high score.

Finding out if a number is less than 10 to give a special message.

Comparing two dates to see which comes first.

Checking if two strings are the same to avoid duplicates.

Syntax

Swift

a == b   // equal to
a != b   // not equal to
a > b    // greater than
a < b    // less than
a >= b   // greater than or equal to
a <= b   // less than or equal to

Use these operators inside conditions like if or while to control the flow.

They return a Bool value: true or false.

Examples

Checks if x equals y. Here, 5 is not equal to 10, so it prints false.

Swift

let x = 5
let y = 10
print(x == y)  // false

Checks if a is greater than b. Since 7 is greater than 3, it prints true.

Swift

let a = 7
let b = 3
print(a > b)   // true

Checks if two strings are not equal. They are equal, so it prints false.

Swift

let name1 = "Anna"
let name2 = "Anna"
print(name1 != name2)  // false

Sample Program

This program checks the temperature and prints a message based on comparison operators.

Swift

let temperature = 30
if temperature > 25 {
    print("It's hot outside!")
} else if temperature == 25 {
    print("It's warm today.")
} else {
    print("It's cool outside.")
}

Important Notes

Remember that == checks for equality, not assignment.

Use parentheses () to group comparisons if needed for clarity.

Summary

Comparison operators compare two values and return true or false.

They are used to make decisions in code, like in if statements.

Common operators include ==, !=, >, <, >=, and <=.

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