Ternary operator in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple ternary expression

What is the output of this Ruby code?

Ruby

result = 5 > 3 ? "yes" : "no"
puts result

A true

B no

C yes

D false

💡 Hint

The ternary operator chooses the first value if the condition is true.

Since 5 is greater than 3, the condition is true, so the expression returns "yes".

❓ Predict Output

intermediate

Ternary operator with numeric result

What will be the output of this Ruby code?

Ruby

num = 10
result = num.even? ? num / 2 : num * 3
puts result

A 20

B 30

C 10

D 5

💡 Hint

Check if the number is even and then apply the correct operation.

10 is even, so the expression returns 10 / 2 which is 5.

❓ Predict Output

advanced

Nested ternary operator output

What is the output of this Ruby code with nested ternary operators?

Ruby

score = 75
result = score > 90 ? "A" : score > 80 ? "B" : score > 70 ? "C" : "F"
puts result

A C

B B

C A

D F

💡 Hint

Evaluate conditions from left to right carefully.

75 is not greater than 90 or 80, but it is greater than 70, so the result is "C".

❓ Predict Output

advanced

Ternary operator with method call

What will this Ruby code output?

Ruby

def check(num)
  num > 0 ? "positive" : "non-positive"
end
puts check(-1)

A error

B non-positive

C nil

D positive

💡 Hint

Check the condition num > 0 for -1.

Since -1 is not greater than 0, the ternary returns "non-positive".

🧠 Conceptual

expert

Understanding ternary operator precedence

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

Ruby

x = false || true ? 1 : 2

A 1

B 2

C true

D false

💡 Hint

Remember that ternary operator has higher precedence than || operator.

The expression is evaluated as false || (true ? 1 : 2). The ternary returns 1, so false || 1 is 1 (truthy), and in Ruby, || returns the first truthy value, which is 1, so x is 1.

Practice

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

easy

A. It chooses one of two values based on a condition.

B. It creates a loop that runs twice.

C. It defines a new method.

D. It comments out a line of code.

Solution

1. Step 1: Understand the ternary operator syntax

   The ternary operator uses a condition followed by a question mark, then the value if true, a colon, and the value if false.

2. Step 2: Identify its purpose

   This syntax means it picks one of two values depending on whether the condition is true or false.

3. Final Answer:

   It chooses one of two values based on a condition. -> Option A

4. Quick Check:

   condition ? true_value : false_value = chooses value [OK]

Hint: Remember: condition ? true : false picks one value fast [OK]

Common Mistakes:

• Thinking it creates loops
• Confusing it with method definitions
• Believing it comments code

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 the ternary operator format

   The correct format is condition followed by a question mark, then the true value, a colon, and the false value.

2. Step 2: Compare options

   Only condition ? value_if_true : value_if_false matches this exact syntax; others misuse punctuation or order.

3. Final Answer:

   condition ? value_if_true : value_if_false -> Option A

4. Quick Check:

   Syntax = condition ? true : false [OK]

Hint: Question mark then colon separate true and false parts [OK]

Common Mistakes:

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

3. What is the output of this Ruby code?

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

medium

A. Minor

B. 20

C. SyntaxError

D. Adult

Solution

1. Step 1: Evaluate the condition age >= 18

   Since age is 20, which is greater than or equal to 18, the condition is true.

2. Step 2: Apply the ternary operator

   Because the condition is true, message is assigned "Adult".

3. Final Answer:

   Adult -> Option D

4. Quick Check:

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

Hint: Check condition result first, then pick true or false value [OK]

Common Mistakes:

• Choosing the false value by mistake
• Printing the variable instead of its value
• Confusing syntax errors

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

score = 75
result = score > 60 ? "Pass" "Fail"
puts result

medium

A. Wrong variable name

B. Missing colon between true and false values

C. Missing question mark after condition

D. Using double quotes incorrectly

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 : false [OK]

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

Common Mistakes:

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

5. You want to assign a variable status based on a number n: if n is positive, assign "Positive"; if zero, assign "Zero"; else assign "Negative". Which Ruby code using ternary operators is correct?

hard

A. status = n > 0 ? "Positive" : n == 0 ? "Zero" "Negative"

B. status = n > 0 ? "Positive" : "Zero" ? n == 0 : "Negative"

C. status = n > 0 ? "Positive" : (n == 0 ? "Zero" : "Negative")

D. status = (n > 0 ? "Positive" : "Zero") ? n == 0 : "Negative"

Solution

1. Step 1: Understand nested ternary operator usage

   To handle three cases, nest one ternary inside the false part of another, using parentheses for clarity.

2. Step 2: Analyze each option

   status = n > 0 ? "Positive" : (n == 0 ? "Zero" : "Negative") correctly nests the second ternary inside parentheses, ensuring proper evaluation order.

3. Final Answer:

   status = n > 0 ? "Positive" : (n == 0 ? "Zero" : "Negative") -> Option C

4. Quick Check:

   Nested ternary with parentheses = correct [OK]

Hint: Use parentheses to nest ternary operators clearly [OK]

Common Mistakes:

• Missing parentheses causing wrong evaluation
• Misplacing question marks and colons
• Confusing order of conditions