Ternary operator usage in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assign 'even' if number is divisible by 2, otherwise 'odd'.

Ruby

result = number % 2 == 0 ? [1] : 'odd'

Drag options to blanks, or click blank then click option'

A'even'

B'odd'

C'zero'

D'none'

Attempts:

3 left

💡 Hint

Common Mistakes

Putting 'odd' before the colon instead of 'even'.

Forgetting quotes around the string.

The ternary operator checks if number is divisible by 2. If true, it assigns 'even', else 'odd'.

2fill in blank

medium

Complete the code to assign 'adult' if age is 18 or more, otherwise 'minor'.

Ruby

status = age >= 18 ? [1] : 'minor'

Drag options to blanks, or click blank then click option'

A'child'

B'adult'

C'teen'

D'senior'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'child' or 'teen' instead of 'adult'.

Confusing the true and false parts.

If age is 18 or more, the ternary operator assigns 'adult', else 'minor'.

3fill in blank

hard

Fix the error in the ternary operator to assign 'positive' if num > 0, else 'non-positive'.

Ruby

label = num > 0 ? [1] : 'non-positive'

Drag options to blanks, or click blank then click option'

Atrue

Bpositive

Cnum

D'positive'

Attempts:

3 left

💡 Hint

Common Mistakes

Missing quotes around 'positive'.

Using a variable name instead of a string.

The true part must be a string 'positive' with quotes, not a bare word.

4fill in blank

hard

Fill both blanks to assign 'even' if n is divisible by 2, else 'odd'.

Ruby

result = n % 2 [1] 0 ? 'even' : [2]

Drag options to blanks, or click blank then click option'

A==

B!=

C'odd'

D'even'

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' instead of '=='.

Swapping 'even' and 'odd' in the false part.

The condition checks if n % 2 equals 0. If true, 'even' else 'odd'.

5fill in blank

hard

Fill all three blanks to assign 'positive', 'negative', or 'zero' based on the value of val.

Ruby

label = val > 0 ? [1] : val < 0 ? [2] : [3]

Drag options to blanks, or click blank then click option'

A'positive'

B'negative'

C'zero'

D'none'

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the order of conditions.

Forgetting quotes around strings.

Nested ternary checks val > 0 for 'positive', val < 0 for 'negative', else 'zero'.

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