Comparison operators in Kotlin - Step-by-Step Execution

Concept Flow - Comparison operators

Start

↓

Evaluate left operand

↓

Evaluate right operand

↓

Apply comparison operator

↓

Result: true or false

↓

Use result in condition or expression

↓

End

The program evaluates two values, compares them using an operator, and produces true or false as the result.

Execution Sample

Kotlin

fun main() {
    val a = 5
    val b = 3
    val result = a > b
    println(result)
}

This code compares two numbers and prints true if the first is greater than the second.

Execution Table

Step	Action	Evaluation	Result
1	Assign a = 5	a = 5	5
2	Assign b = 3	b = 3	3
3	Compare a > b	5 > 3	true
4	Assign result = true	result = true	true
5	Print result	println(true)	true

💡 Program ends after printing the comparison result.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 4	Final
a	undefined	5	5	5	5
b	undefined	undefined	3	3	3
result	undefined	undefined	undefined	true	true

Key Moments - 3 Insights

Why does the comparison a > b return true when a is 5 and b is 3?

Because 5 is greater than 3, the comparison a > b evaluates to true as shown in execution_table step 3.

What type of value does a comparison operator produce?

Comparison operators produce a Boolean value: true or false, as seen in the result variable in execution_table step 4.

Can comparison operators be used with variables that hold numbers?

Yes, comparison operators compare the values stored in variables, like a and b in steps 1 and 2, to produce true or false.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what is the result of the comparison a > b?

A true

B false

C 5

D 3

💡 Hint

Check the 'Result' column in execution_table row 3.

At which step is the variable 'result' assigned a value?

A Step 2

B Step 4

C Step 3

D Step 5

💡 Hint

Look at the 'Action' column for assignment to 'result' in execution_table.

If we change b to 7, what would be the result of a > b at step 3?

A true

B 5

C false

D 7

💡 Hint

Compare values 5 and 7 using > operator as in execution_table step 3.

Concept Snapshot

Comparison operators in Kotlin compare two values.
They return true or false.
Common operators: >, <, >=, <=, ==, !=.
Used in conditions and expressions.
Example: val result = a > b
result is Boolean.

Full Transcript

This lesson shows how Kotlin compares two values using comparison operators. The program assigns 5 to variable a and 3 to variable b. Then it compares if a is greater than b using the > operator. The comparison produces true because 5 is greater than 3. This true value is stored in the variable result and printed. Comparison operators always return true or false, which can be used in conditions or other expressions. The execution table traces each step: assigning variables, comparing values, storing the result, and printing it. The variable tracker shows how a, b, and result change during execution. Key moments clarify why the comparison returns true and what type of value it produces. The quiz tests understanding of the comparison result, assignment step, and effect of changing values.

Practice

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

easy

A. <=

B. !=

C. >

D. ==

Solution

1. Step 1: Understand the meaning of comparison operators

   In Kotlin, the operator == is used to check if two values are equal.

2. Step 2: Identify the correct operator for equality

   The operator == returns true if both values are equal, otherwise false.

3. Final Answer:

   == -> Option D

4. Quick Check:

   Equality operator = == [OK]

Hint: Remember: '==' means equal, '!=' means not equal [OK]

Common Mistakes:

• Confusing '==' with '=' which is assignment
• Using '!=' to check equality
• Mixing up '>' and '<=' operators

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

easy

A. a != b

B. a <> b

C. a =! b

D. a !== b

Solution

1. Step 1: Recall Kotlin syntax for inequality

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

2. Step 2: Verify each option

   a != b is correct; a <> b is invalid in Kotlin; a =! b is incorrect syntax; a !== b checks referential inequality, not value inequality.

3. Final Answer:

   a != b -> Option A

4. Quick Check:

   Not equal operator = != [OK]

Hint: Use '!=' for not equal, never '<>' in Kotlin [OK]

Common Mistakes:

• Using '<>' which is not valid in Kotlin
• Swapping '=' and '!' in 'a =! b'
• Confusing '!=' with '!==', which checks references

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

val x = 10
val y = 20
println(x > y)

medium

A. false

B. true

C. 10

D. Compilation error

Solution

1. Step 1: Evaluate the comparison expression

   The expression x > y compares if 10 is greater than 20, which is false.

2. Step 2: Understand the println output

   Printing the boolean result of the comparison will output false.

3. Final Answer:

   false -> Option A

4. Quick Check:

   10 > 20 = false [OK]

Hint: Compare values carefully; 10 is not greater than 20 [OK]

Common Mistakes:

• Assuming 10 > 20 is true
• Confusing output with variable values
• Expecting a number instead of boolean output

4. Identify the error in this Kotlin code snippet:

val a = 5
val b = 10
if (a = b) {
    println("Equal")
} else {
    println("Not Equal")
}

medium

A. Variables a and b must be mutable

B. Missing semicolon after println

C. Using '=' instead of '==' in if condition

D. Incorrect println syntax

Solution

1. Step 1: Check the if condition syntax

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

2. Step 2: Correct the operator for comparison

   Use == to compare values, so it should be a == b.

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 '=' in if condition instead of '=='
• Thinking semicolons are required in Kotlin
• Assuming val variables must be mutable for comparison

5. Given the Kotlin code below, what will be the output?

val a = 7
val b = 7
val c = 10
println((a == b) && (b < c))

hard

A. false

B. true

C. 7

D. Compilation error

Solution

1. Step 1: Evaluate the first comparison (a == b)

   Since both a and b are 7, a == b is true.

2. Step 2: Evaluate the second comparison (b < c)

   Since 7 is less than 10, b < c is true.

3. Step 3: Evaluate the logical AND

   Both conditions are true, so true && true is true.

4. Final Answer:

   true -> Option B

5. Quick Check:

   (7 == 7) && (7 < 10) = true [OK]

Hint: Both conditions must be true for && to return true [OK]

Common Mistakes:

• Confusing && with || operator
• Misreading comparison results
• Expecting numeric output instead of boolean