Loop method for infinite loops in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple infinite loop with break

What is the output of this Ruby code?

Ruby

count = 0
loop do
  puts count
  count += 1
  break if count == 3
end

A

0
1
2

B

0
1
2
3

C

1
2
3

D No output, infinite loop

💡 Hint

The loop stops when count reaches 3, so it prints before breaking.

The loop prints count starting at 0, increments it, and breaks when count equals 3. So it prints 0, 1, 2 and then stops.

❓ Predict Output

intermediate

Loop method with next keyword

What will this Ruby code print?

Ruby

i = 0
loop do
  i += 1
  next if i.even?
  puts i
  break if i >= 5
end

A No output, infinite loop

B

2
4
6

C

1
2
3
4
5

D

1
3
5

💡 Hint

The next keyword skips even numbers.

The loop increments i, skips printing if i is even, prints odd numbers, and stops when i reaches 5.

🔧 Debug

advanced

Identify the error in this infinite loop

What error does this Ruby code produce?

Ruby

loop do
  puts "Hello"
  break if false
end

A RuntimeError: break from proc-closure

B SyntaxError

C No error, infinite loop printing "Hello" forever

D NameError

💡 Hint

The break condition is always false, so the loop never stops.

The break condition is false, so the loop never breaks and prints "Hello" forever without error.

🧠 Conceptual

advanced

Behavior of loop with return inside

What is the value of variable result after running this Ruby code?

Ruby

result = loop do
  break 42
end

A 42

B nil

C true

D Raises an error

💡 Hint

The break keyword can return a value from the loop.

In Ruby, break can return a value from the loop, so result gets the value 42.

❓ Predict Output

expert

Output of nested loops with break and next

What is the output of this Ruby code?

Ruby

i = 0
loop do
  i += 1
  j = 0
  loop do
    j += 1
    break if j > 2
    next if j == 1
    puts "i=#{i}, j=#{j}"
  end
  break if i >= 2
end

A No output, infinite loop

B

i=1, j=2
i=2, j=2

C i=1, j=2

D

i=1, j=1
i=1, j=2
i=2, j=1
i=2, j=2

💡 Hint

The inner loop skips j=1 and breaks after j>2; outer loop runs twice.

For each i (1 and 2), inner loop increments j from 1 to 3. It skips printing when j=1, prints when j=2, then breaks when j>2. So output lines are for j=2 for i=1 and i=2.

Practice

1. What does the Ruby code loop do; puts "Hello"; break; end do?

easy

A. Prints "Hello" once and stops the loop

B. Prints "Hello" infinitely without stopping

C. Causes a syntax error

D. Prints nothing

Solution

1. Step 1: Understand the loop structure

   The loop do ... end creates an infinite loop that repeats the code inside.

2. Step 2: Analyze the break statement

   The break immediately stops the loop after printing "Hello" once.

3. Final Answer:

   Prints "Hello" once and stops the loop -> Option A

4. Quick Check:

   loop with break stops after one iteration [OK]

Hint: Remember: break stops the infinite loop immediately [OK]

Common Mistakes:

• Thinking loop runs forever even with break
• Confusing loop with while
• Ignoring the break statement

2. Which of the following is the correct syntax to create an infinite loop using the loop method in Ruby?

easy

A. loop: do puts "Hi" end

B. loop { puts "Hi" do end }

C. loop puts "Hi" do end

D. loop { puts "Hi" }

Solution

1. Step 1: Review Ruby loop syntax

   The loop method can take a block with curly braces or do...end.

2. Step 2: Identify correct syntax

   loop { puts "Hi" } uses loop { puts "Hi" }, which is valid Ruby syntax for an infinite loop.

3. Final Answer:

   loop { puts "Hi" } -> Option D

4. Quick Check:

   loop with block braces is valid syntax [OK]

Hint: Use loop with { } or do...end for blocks [OK]

Common Mistakes:

• Placing do after loop without block
• Using colon incorrectly
• Missing block braces or do...end

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

count = 0
loop do
  puts count
  count += 1
  break if count == 3
end

medium

A. 0 1 2 3

B. 0 1 2

C. 1 2 3

D. Infinite loop printing numbers

Solution

1. Step 1: Trace the loop iterations

   Initially, count = 0. The loop prints count, then increments it by 1.

2. Step 2: Check break condition

   Loop breaks when count == 3, so it stops after printing 0, 1, and 2.

3. Final Answer:

   0 1 2 -> Option B

4. Quick Check:

   Loop stops before printing 3 due to break condition [OK]

Hint: Break stops loop before count reaches 3 [OK]

Common Mistakes:

• Including 3 in output
• Forgetting to increment count
• Assuming infinite loop

4. Identify the error in the following Ruby code using loop do:

loop do
  puts "Start"
  break
  puts "End"
end

medium

A. The code after break will never execute

B. The break statement is unreachable

C. Syntax error due to missing end

D. Infinite loop without break

Solution

1. Step 1: Understand break behavior

   The break stops the loop immediately when reached.

2. Step 2: Analyze code after break

   The puts "End" after break will never run because break exits the loop first.

3. Final Answer:

   The code after break will never execute -> Option A

4. Quick Check:

   Code after break is skipped [OK]

Hint: Code after break inside loop is ignored [OK]

Common Mistakes:

• Thinking code after break runs
• Confusing break with next
• Assuming syntax error

5. How can you use the Ruby loop do method to repeatedly ask a user for input until they type "exit"?

hard

A. Use loop without break and rely on user to close program

B. Use while loop with condition input != "exit"

C. Use loop with gets and break if input equals "exit"

D. Use for loop iterating over input strings

Solution

1. Step 1: Use loop to repeat input request

   The loop do method runs code repeatedly until broken.

2. Step 2: Use break with condition on user input

   Inside the loop, get user input with gets.chomp and break if input is "exit".

3. Final Answer:

   Use loop with gets and break if input equals "exit" -> Option C

4. Quick Check:

   loop + break on condition = controlled infinite loop [OK]

Hint: Break loop when input matches exit string [OK]

Common Mistakes:

• Not using break to stop loop
• Using wrong loop type
• Forgetting to remove newline from input