Break, next, and redo behavior in Ruby - Step-by-Step Execution

Concept Flow - Break, next, and redo behavior

Start Loop

↓

Check Condition

Yes↓

Inside Loop Body

↓

next?

Yes→Skip to Next Iteration

↓

redo?

Yes→Repeat Current Iteration

↓

break?

Yes→Exit Loop

↓

Continue Loop

↓

End Loop

The loop starts and checks the condition. Inside the loop, 'next' skips to the next iteration, 'redo' repeats the current iteration, and 'break' exits the loop immediately.

Execution Sample

Ruby

i = 0
loop do
  i += 1
  next if i == 2
  puts i
  break if i == 4
  redo if i == 3
end

This Ruby loop increments i, skips printing when i is 2, repeats the iteration when i is 3 (incrementing i to 4 on redo), and stops when i reaches 4. Output: 1 3 4

Execution Table

Step	i value	Condition	Action	Output
1	0 -> 1	i == 2? No	print 1, no break, no redo	1
2	1 -> 2	i == 2? Yes	next: skip print/break/redo
3	2 -> 3	i == 2? No	print 3, no break, redo triggers	3
4 (redo)	3 -> 4	i == 2? No	print 4, break triggers	4
5			exit loop

💡 Loop exits because i == 4 triggers break

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
i	0	1	2	3	4	4

Key Moments - 3 Insights

Why does i increase from 3 to 4 during the redo?

'redo' restarts the entire loop body from the top without re-checking the condition, so the 'i += 1' executes again, incrementing i to 4 (step 4).

Why is nothing printed when i equals 2?

The 'next' statement skips the rest of the loop body for that iteration, so the print statement is not executed (step 2).

What causes the loop to stop?

When i reaches 4 during the redo (step 4), the 'break' statement runs, immediately exiting the loop.

Visual Quiz - 3 Questions

Look at the execution table, what is the i value change at step 4?

A 2 -> 3

B 1 -> 2

C 3 -> 4

D 0 -> 1

💡 Hint

Check the 'i value' column for step 4 in the execution_table.

At which step does the loop skip printing the value of i?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for the 'next' action in the Action column of the execution_table.

If the 'redo' line was removed, what would be printed after 3?

A 4

B 2

C Nothing, breaks

D Infinite 3

💡 Hint

Without 'redo', after printing 3 the loop continues to next iteration: i=4, print 4, break.

Concept Snapshot

Ruby loop control keywords:
- break: exits the loop immediately
- next: skips to the next iteration
- redo: repeats the current iteration without re-evaluating condition (re-executes body from start)
Use these inside loops to control flow precisely.

Full Transcript

This example shows a Ruby loop where i starts at 0. It prints 1, skips 2 with 'next', prints 3 then 'redo' which re-executes the body (i to 4, prints 4, breaks). The execution table traces each step accurately, showing how 'redo' increments i. Variable tracker shows i changes. Key moments explain redo increments because body restarts at 'i += 1'. Quiz tests step values and behaviors. Helps understand 'break', 'next', 'redo' in Ruby loops.

Practice

1. What does the break keyword do inside a Ruby loop?

easy

A. Stops the loop completely and exits it

B. Skips the current iteration and moves to the next

C. Repeats the current iteration without moving forward

D. Pauses the loop until a condition is met

Solution

1. Step 1: Understand the role of break

   The break keyword immediately stops the loop and exits it, no further iterations happen.

2. Step 2: Compare with other keywords

   next skips to the next iteration, redo repeats the current one, but break stops all looping.

3. Final Answer:

   Stops the loop completely and exits it -> Option A

4. Quick Check:

   break = stop loop [OK]

Hint: Break means stop the loop right away [OK]

Common Mistakes:

• Confusing break with next
• Thinking break repeats iteration
• Assuming break pauses instead of stops

2. Which of the following is the correct syntax to skip the current iteration in a Ruby loop?

easy

A. break

B. next

C. redo

D. skip

Solution

1. Step 1: Identify the keyword for skipping iteration

   The keyword next is used in Ruby to skip the rest of the current loop iteration and move to the next one.

2. Step 2: Check other options

   break stops the loop, redo repeats the current iteration, and skip is not a Ruby keyword.

3. Final Answer:

   next -> Option B

4. Quick Check:

   Skip iteration = next [OK]

Hint: Use next to jump to next loop step [OK]

Common Mistakes:

• Using break instead of next
• Trying to use skip keyword (not valid)
• Confusing redo with next

3. What is the output of this Ruby code?

i = 0
while i < 3
  i += 1
  if i == 2
    redo
  end
  puts i
end

medium

A. 1 2 2 2 ... (infinite loop)

B. 1 3

C. 1 2 3

D. 1 3 3

Solution

1. Step 1: Trace the loop and redo behavior

   When i == 2, redo repeats the current iteration without incrementing i again, causing the loop to print 2 repeatedly.

2. Step 2: Understand infinite repetition

   Since i is not changed inside the redo loop, it never moves past 2, causing an infinite loop printing 2 repeatedly.

3. Final Answer:

   1 2 2 2 ... (infinite loop) -> Option A

4. Quick Check:

   redo repeats current step causing infinite loop [OK]

Hint: Redo repeats current step, watch for infinite loops [OK]

Common Mistakes:

• Assuming i increments inside redo
• Thinking redo skips iteration
• Ignoring infinite loop possibility

4. Find the error in this Ruby code snippet:

for i in 1..3
  if i == 2
    next
  elsif i == 3
    redo
  end
  puts i
end

medium

A. puts should be before if statement

B. next cannot be used inside for loops

C. Syntax error: missing end for if

D. Using redo inside for loop causes infinite loop

Solution

1. Step 1: Analyze the use of redo in the loop

   The redo inside the elsif i == 3 causes the loop to repeat the same iteration infinitely because i does not change.

2. Step 2: Check other options for errors

   next works fine in for loops, the if statement is properly closed, and puts can be after if.

3. Final Answer:

   Using redo inside for loop causes infinite loop -> Option D

4. Quick Check:

   Redo repeats current step causing infinite loop [OK]

Hint: Redo without changing loop variable causes infinite loop [OK]

Common Mistakes:

• Thinking next is invalid in for loops
• Missing that redo repeats without increment
• Assuming syntax error due to indentation

5. You want to print numbers 1 to 5 but skip 3 and repeat printing 4 twice using next and redo. Which code achieves this correctly?

i = 0
while i < 5
  i += 1
  if i == 3
    # skip 3
  elsif i == 4
    # print 4 twice
  end
  puts i
end

hard

A. if i == 3
next
elsif i == 4
puts i
redo
next
end

B. if i == 3
next
elsif i == 4
redo
end

C. if i == 3
next
elsif i == 4
puts i
redo
end

D. if i == 3
redo
elsif i == 4
next
end

Solution

1. Step 1: Skip number 3 using next

   Using next when i == 3 skips printing 3 and moves to next iteration.

2. Step 2: Repeat printing 4 twice using redo

   When i == 4, print it once, then use redo to repeat the iteration and print 4 again.

3. Step 3: Verify code correctness

   if i == 3 next elsif i == 4 puts i redo end prints 4, then calls redo to repeat printing 4, and skips 3 correctly. Other options misuse next or redo causing errors or infinite loops.

4. Final Answer:

   if i == 3 next elsif i == 4 puts i redo end -> Option C

5. Quick Check:

   next skips, redo repeats current step [OK]

Hint: Use next to skip, redo after puts to repeat [OK]

Common Mistakes:

• Calling redo before puts causing infinite loop
• Using next after redo incorrectly
• Not skipping 3 properly