Sequence creation methods in Kotlin - Step-by-Step Execution

Concept Flow - Sequence creation methods

Start

↓

Choose creation method

↓

sequenceOf(elements)

↓

generateSequence(seed) { next }

↓

sequence builder { yield() }

↓

Use sequence

↓

End

You start by choosing a method to create a sequence, then use it as needed.

Execution Sample

Kotlin

val seq = sequenceOf(1, 2, 3)
for (num in seq) {
  println(num)
}

Creates a sequence from given elements and prints each number.

Execution Table

Step	Action	Sequence State	Output
1	Create sequenceOf(1, 2, 3)	[1, 2, 3]
2	Start iteration	[1, 2, 3]
3	Yield first element	[2, 3]	1
4	Yield second element	[3]	2
5	Yield third element	[]	3
6	Iteration ends	[]

💡 All elements yielded, sequence is empty, iteration stops.

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
seq	[1, 2, 3]	[2, 3]	[3]	[]	[]
num	undefined	1	2	3	3

Key Moments - 2 Insights

Why does the sequence become empty after iteration?

Because sequenceOf yields each element one by one and removes it from the remaining sequence, as shown in execution_table rows 3-5.

What happens if you try to iterate the sequence again?

The sequence is already consumed (empty), so no elements will be yielded again, similar to the final state in variable_tracker.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what is the output?

A 2

B 3

C 1

D No output

💡 Hint

Check the Output column at step 3 in execution_table.

At which step does the sequence become empty?

A Step 4

B Step 5

C Step 6

D Step 3

💡 Hint

Look at the Sequence State column in execution_table to see when it becomes [].

If you add another element to sequenceOf, how does variable 'seq' change after first yield?

A It removes the first element only

B It removes all elements

C It stays the same

D It becomes empty immediately

💡 Hint

Refer to variable_tracker showing how 'seq' changes after each yield.

Concept Snapshot

Sequence creation methods in Kotlin:
- sequenceOf(vararg elements): creates a sequence from given elements.
- generateSequence(seed) { next }: creates sequence by generating next values.
- sequence builder { yield() }: builds sequence lazily.
Sequences produce elements one by one when iterated.

Full Transcript

This visual trace shows how Kotlin sequences are created and used. We start by creating a sequence using sequenceOf with elements 1, 2, 3. The sequence holds these elements initially. When we iterate, each element is yielded one by one, and the sequence state updates by removing the yielded element. After all elements are yielded, the sequence becomes empty and iteration stops. Variables track these changes step by step. Common confusions include why the sequence becomes empty and what happens if iterated again. The quiz questions help reinforce understanding by referencing the execution steps and variable states.