Repeat-while loop in Swift - Step-by-Step Execution

Concept Flow - Repeat-while loop

Start

↓

Execute loop body

↓

Check condition

↓

Exit loop

The repeat-while loop runs the code inside first, then checks the condition. If true, it repeats; if false, it stops.

Execution Sample

Swift

var count = 1
repeat {
  print(count)
  count += 1
} while count <= 3

This code prints numbers 1 to 3 using a repeat-while loop.

Execution Table

Step	count value	Condition (count <= 3)	Action	Output
1	1	true	Print 1, count = 2	1
2	2	true	Print 2, count = 3	2
3	3	true	Print 3, count = 4	3
4	4	false	Exit loop

💡 count becomes 4, condition 4 <= 3 is false, so loop stops

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
count	1	2	3	4	4

Key Moments - 2 Insights

Why does the loop body run even when the condition is false at the start?

Because repeat-while checks the condition after running the loop body once, so the body always runs at least once (see execution_table step 1).

What happens if the condition is false right after the first loop execution?

The loop stops after that first execution, as shown in execution_table step 4 where condition is false and loop exits.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of count at step 3?

A 4

B 3

C 2

D 1

💡 Hint

Check the 'count value' column at step 3 in the execution_table.

At which step does the condition become false and the loop stops?

A Step 4

B Step 2

C Step 3

D Step 1

💡 Hint

Look at the 'Condition' column in execution_table and find where it is false.

If we change the condition to count < 3, how many times will the loop run?

A 3 times

B 1 time

C 2 times

D 4 times

💡 Hint

Refer to variable_tracker and think when count < 3 becomes false.

Concept Snapshot

repeat {
  // code to run
} while condition

- Runs loop body first, then checks condition
- Repeats while condition is true
- Always runs at least once
- Use when loop must run before condition check

Full Transcript

The repeat-while loop in Swift runs the code inside the loop first, then checks the condition. If the condition is true, it repeats the loop. If false, it stops. This means the loop body always runs at least once, even if the condition is false at the start. For example, with count starting at 1, the loop prints count and increases it by 1 each time. It stops when count becomes 4 because 4 <= 3 is false. The variable count changes from 1 to 4 through the loop. This loop is useful when you want to run code first and then decide if it should repeat.