Ternary operator usage in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby code using ternary operator?

Consider the following Ruby code snippet. What will it print?

Ruby

x = 5
puts x > 3 ? "Greater" : "Smaller"

A false

B Smaller

C true

D Greater

💡 Hint

Check if x is greater than 3 and what the ternary operator returns.

Since x is 5, which is greater than 3, the condition is true, so the first string "Greater" is printed.

❓ Predict Output

intermediate

What does this nested ternary operator print?

Analyze the output of this Ruby code with nested ternary operators.

Ruby

a = 10
b = 20
puts a > b ? "a is bigger" : a == b ? "equal" : "b is bigger"

A b is bigger

B a is bigger

C equal

D SyntaxError

💡 Hint

Check the first condition a > b, then the second condition a == b.

Since 10 > 20 is false, it checks a == b which is also false, so it prints "b is bigger".

🔧 Debug

advanced

What error does this Ruby code raise?

Identify the error raised by this Ruby code snippet using ternary operator.

Ruby

num = 7
result = num > 5 ? "High" :
"Low"
puts result

A No error, prints High

B SyntaxError

C No error, prints Low

D NameError

💡 Hint

Check if the line break affects the ternary operator syntax.

Ruby allows line breaks after the ? operator if the expression continues, so no error occurs and since num is 7 > 5, it prints High.

❓ Predict Output

advanced

What is the value of variable 'output' after running this code?

Determine the value stored in 'output' after this Ruby code executes.

Ruby

value = nil
output = value ? "Exists" : "Nil or false"
puts output

A Exists

B Nil or false

C nil

D false

💡 Hint

Remember how Ruby treats nil in conditionals.

In Ruby, false and nil are falsy. value is nil, which is falsy, so the ternary returns "Nil or false".

❓ Predict Output

expert

What is the output of this Ruby code with complex ternary and method call?

Analyze the output of this Ruby code snippet.

Ruby

def check(num)
  num.even? ? "Even" : num > 10 ? "Odd and big" : "Odd and small"
end

puts check(7)

A Even

B Odd and big

C Odd and small

D NoMethodError

💡 Hint

Check the method call and nested ternary logic carefully.

7 is odd (not even), so first condition false, then checks if 7 > 10 (false), so returns "Odd and small".

Practice

1. What does the ternary operator condition ? value_if_true : value_if_false do in Ruby?

easy

A. It chooses one of two values based on the condition's truth.

B. It creates a loop that runs twice.

C. It defines a new method with two parameters.

D. It comments out the code after the colon.

Solution

1. Step 1: Understand the ternary operator format

   The ternary operator uses a condition followed by a question mark, then two values separated by a colon.

2. Step 2: Identify its purpose

   It returns the first value if the condition is true, otherwise the second value.

3. Final Answer:

   It chooses one of two values based on the condition's truth. -> Option A

4. Quick Check:

   condition ? true_value : false_value = chooses value [OK]

Hint: Think: condition true? pick first value, else second [OK]

Common Mistakes:

• Confusing ternary with loops
• Thinking it defines methods
• Misunderstanding the colon as comment

2. Which of the following is the correct syntax for a ternary operator in Ruby?

easy

A. condition ? value_if_true : value_if_false

B. condition : value_if_true ? value_if_false

C. condition ? value_if_true ; value_if_false

D. condition ? value_if_true, value_if_false

Solution

1. Step 1: Recall ternary operator syntax

   The correct syntax places a question mark after the condition, then the true value, a colon, then the false value.

2. Step 2: Compare options

   Only condition ? value_if_true : value_if_false matches the correct format: condition ? true_value : false_value.

3. Final Answer:

   condition ? value_if_true : value_if_false -> Option A

4. Quick Check:

   Syntax = condition ? true : false [OK]

Hint: Remember: question mark before true, colon before false [OK]

Common Mistakes:

• Swapping question mark and colon
• Using semicolon instead of colon
• Separating values with comma

3. What is the output of this Ruby code?

age = 20
puts age >= 18 ? "Adult" : "Minor"

medium

A. Minor

B. 20

C. SyntaxError

D. Adult

Solution

1. Step 1: Evaluate the condition

   The condition age >= 18 is true because age is 20.

2. Step 2: Apply ternary operator

   Since the condition is true, the expression returns "Adult".

3. Final Answer:

   Adult -> Option D

4. Quick Check:

   20 >= 18 ? "Adult" : "Minor" = "Adult" [OK]

Hint: Check condition true? pick first value, else second [OK]

Common Mistakes:

• Choosing the false value by mistake
• Printing the variable instead of result
• Expecting syntax error

4. Identify the error in this Ruby code using a ternary operator:

score = 85
result = score > 60 ? "Pass" "Fail"
puts result

medium

A. Missing question mark after condition

B. Missing colon between true and false values

C. Ternary operator cannot be used with strings

D. Wrong variable name 'score'

Solution

1. Step 1: Check ternary operator syntax

   The ternary operator requires a colon between the true and false values.

2. Step 2: Identify missing colon

   The code has "Pass" "Fail" without a colon, causing a syntax error.

3. Final Answer:

   Missing colon between true and false values -> Option B

4. Quick Check:

   Syntax = condition ? true_value : false_value [OK]

Hint: Always put colon between true and false parts [OK]

Common Mistakes:

• Omitting colon
• Using comma instead of colon
• Forgetting question mark

5. Given this Ruby code, what will be the output?

values = [0, 1, nil, 5]
results = values.map { |v| v ? "Yes" : "No" }
puts results.inspect

hard

A. ["No", "Yes", "No", "Yes"]

B. ["No", "No", "No", "No"]

C. ["Yes", "Yes", "No", "Yes"]

D. ["Yes", "No", "Yes", "No"]

Solution

1. Step 1: Understand truthiness in Ruby

   In Ruby, 0 and 1 are truthy, nil is falsy.

2. Step 2: Apply ternary operator to each element

   For each value: 0 (truthy) -> "Yes", 1 (truthy) -> "Yes", nil (falsy) -> "No", 5 (truthy) -> "Yes".

3. Step 3: Check mapped results

   The results array is ["Yes", "Yes", "No", "Yes"].

4. Final Answer:

   ["Yes", "Yes", "No", "Yes"] -> Option C

5. Quick Check:

   Truthy values = "Yes", nil = "No" [OK]

Hint: Remember: only nil and false are falsey in Ruby [OK]

Common Mistakes:

• Thinking 0 is falsy
• Confusing nil with false
• Misreading map block