Labelled break and continue in Go - Step-by-Step Execution

Concept Flow - Labelled break and continue

Start Outer Loop

↓

Start Inner Loop

↓

Check Condition

↓

Labelled break/continue

↓

Exit or Continue

↩Back to Outer Loop or Exit

The outer loop starts, then the inner loop runs. When a labelled break or continue is hit, control jumps to the labelled loop, either exiting or continuing it.

Execution Sample

Go

Outer:
for i := 1; i <= 3; i++ {
  for j := 1; j <= 3; j++ {
    if j == 2 {
      break Outer
    }
  }
}

This code breaks out of the outer loop when inner loop variable j equals 2.

Execution Table

Step	i	j	Condition j==2?	Action	Loop State
1	1	1	No	Continue inner loop	Inner loop running
2	1	2	Yes	break Outer	Exit outer loop
3	-	-	-	-	Loops terminated

💡 At step 2, j==2 is true, so break Outer exits the outer loop immediately.

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
i	1	1	-	-
j	1	2	-	-

Key Moments - 2 Insights

Why does break Outer exit both loops instead of just the inner loop?

Because the break is labelled with Outer, it tells Go to exit the loop named Outer, not just the current inner loop. See execution_table step 2 where break Outer ends both loops.

What happens if we use continue Outer instead of break Outer?

continue Outer skips the rest of the current iteration of the Outer loop and starts the next iteration. It does not exit the loop. This changes the flow compared to break Outer.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of i when break Outer is executed?

A 1

B 2

C 3

D -

💡 Hint

Check the 'i' column at step 2 in the execution_table.

At which step does the program exit all loops?

A Step 1

B Step 2

C Step 3

D Never

💡 Hint

Look at the 'Action' and 'Loop State' columns in execution_table rows.

If we replace break Outer with continue Outer, what happens at step 2?

A Continue inner loop normally

B Exit both loops

C Skip to next iteration of Outer loop

D Infinite loop

💡 Hint

Refer to key_moments explanation about continue Outer behavior.

Concept Snapshot

Labelled break and continue in Go:
- Use labels to name loops: Label:
- break Label exits the named loop immediately.
- continue Label skips to next iteration of named loop.
- Helps control nested loops clearly.
- Syntax: break Label or continue Label

Full Transcript

This example shows how labelled break and continue work in Go. We have an outer loop named Outer and an inner loop inside it. When the inner loop variable j equals 2, break Outer is executed. This causes the program to exit the outer loop immediately, stopping both loops. The execution table traces each step: at step 1, j is 1 and the loop continues; at step 2, j is 2, condition is true, and break Outer exits the loops. The variable tracker shows how i and j change. Key moments clarify why break Outer exits both loops and what continue Outer would do instead. The visual quiz tests understanding of loop variables and control flow. The snapshot summarizes the syntax and behavior of labelled break and continue in Go.