Pipeline operator concept in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby pipeline code?

Consider the following Ruby code using the pipeline operator |>. What will be printed?

Ruby

result = 5 |> ->(x) { x * 2 } |> ->(x) { x + 3 }
puts result

A 13

B 16

C 10

D 8

💡 Hint

Remember the pipeline operator passes the result of the left expression as the argument to the right lambda.

The number 5 is first doubled to 10, then 3 is added to get 13.

❓ Predict Output

intermediate

What does this pipeline expression return?

Given this Ruby code, what is the value of output?

Ruby

output = 'hello' |> ->(s) { s.upcase } |> ->(s) { s.reverse }
puts output

A HELLO

B OLLEH

C olleh

D hello

💡 Hint

The string is first converted to uppercase, then reversed.

The string 'hello' becomes 'HELLO' after upcase, then reversed to 'OLLEH'.

🔧 Debug

advanced

Why does this pipeline code raise an error?

Look at this Ruby code using the pipeline operator. Why does it raise an error?

Ruby

value = 10 |> ->(x) { x / 0 } |> ->(x) { x + 1 }
puts value

A NoMethodError because the lambda is missing

B SyntaxError because the pipeline operator is used incorrectly

C ZeroDivisionError because dividing by zero is not allowed

D TypeError because 10 is not a valid input

💡 Hint

Think about what happens when you divide a number by zero in Ruby.

Dividing by zero causes a ZeroDivisionError at runtime.

🧠 Conceptual

advanced

What is the main benefit of using the pipeline operator in Ruby?

Choose the best explanation for why the pipeline operator |> is useful in Ruby programming.

A It allows chaining of method calls or functions in a clear, readable way by passing the result of one expression as input to the next.

B It replaces all loops and conditionals with a single operator.

C It automatically parallelizes code execution for faster performance.

D It converts all variables to strings before processing.

💡 Hint

Think about how data flows through chained operations.

The pipeline operator improves readability by making data flow explicit and linear.

📝 Syntax

expert

Which option correctly uses the pipeline operator with a method that takes multiple arguments?

Given a method def add(x, y); x + y; end, which pipeline usage is valid to add 5 and 3?

Ruby

def add(x, y)
  x + y
end

A 5 |> ->(x) { add(3, x) }

B 5 |> add(3)

C 5 |> ->(x, y) { add(x, y) }

D 5 |> ->(x) { add(x, 3) }

💡 Hint

Remember the pipeline operator passes only one argument to the right side.

Option D correctly uses a lambda to accept the pipeline input and calls add with the fixed second argument 3.

Practice

1.

What does the Ruby pipeline operator |> do?

easy

A. It creates a new array from two arrays.

B. It combines two strings into one.

C. It passes the value on the left as the first argument to the method on the right.

D. It comments out the code on the right.

Solution

1. Step 1: Understand the operator's purpose

   The pipeline operator |> takes the value on its left side and sends it as the first argument to the method on its right side.

2. Step 2: Compare with other options

   Options B, C, and D describe unrelated operations like string concatenation, array merging, or commenting, which are not what |> does.

3. Final Answer:

   It passes the value on the left as the first argument to the method on the right. -> Option C

4. Quick Check:

   Pipeline operator = Pass left value as first argument [OK]

Hint: Remember: left value flows into right method as first argument [OK]

Common Mistakes:

• Thinking it concatenates strings
• Confusing it with array merging
• Assuming it comments code

2.

Which of the following is the correct syntax to use the pipeline operator in Ruby?

value ___ method_name

easy

A. |>

B. |

C. ->

D. |>

Solution

1. Step 1: Identify the correct operator symbol

   The Ruby pipeline operator is written as |> without any extra characters or spaces.

2. Step 2: Check each option

   -> uses an arrow -> which is for lambdas, not pipelines. | is just a pipe character, not the pipeline operator. |> has an extra closing tag which is invalid syntax.

3. Final Answer:

   |> -> Option A

4. Quick Check:

   Correct pipeline syntax = |> [OK]

Hint: Look for the exact two-character operator: pipe then greater than [OK]

Common Mistakes:

• Using -> instead of |> operator
• Adding extra characters like
• Missing the greater than symbol

3.

What is the output of the following Ruby code?

def double(x)
  x * 2
end

result = 5 |> double
puts result

medium

A. 25

B. 5double

C. SyntaxError

D. 10

Solution

1. Step 1: Understand the pipeline operation

   The value 5 is passed as the first argument to the method double, so it calls double(5).

2. Step 2: Calculate the method result

   double(5) returns 5 * 2 = 10, so result is 10, which is printed.

3. Final Answer:

   10 -> Option D

4. Quick Check:

   5 |> double = 10 [OK]

Hint: Pipeline passes 5 to double, so output doubles 5 [OK]

Common Mistakes:

• Thinking it concatenates '5' and 'double'
• Expecting a syntax error
• Multiplying 5 by itself instead of 2

4.

Identify the error in this Ruby code using the pipeline operator:

def greet(name)
  "Hello, #{name}!"
end

message = "Alice" |>
  greet
puts message

medium

A. The pipeline operator is missing the right side method.

B. The pipeline operator is split incorrectly across lines.

C. The pipeline operator should be -> instead of |>.

D. The method greet should not use string interpolation.

Solution

1. Step 1: Check pipeline operator usage across lines

   The pipeline operator |> must be on the same line as the left value or properly continued. Here, it is split with a newline after |>, which causes a syntax error.

2. Step 2: Verify other options

   The pipeline operator is missing the right side method. is wrong because the right side method greet is present. The pipeline operator should be -> instead of |>. confuses the operator with lambda syntax. The method greet should not use string interpolation. is unrelated to the pipeline error.

3. Final Answer:

   The pipeline operator is split incorrectly across lines. -> Option B

4. Quick Check:

   Pipeline operator must not be broken by newline [OK]

Hint: Keep pipeline operator and method call on same line [OK]

Common Mistakes:

• Splitting pipeline operator and method on different lines
• Confusing pipeline with lambda syntax
• Blaming string interpolation for error

5.

Given the following methods, what is the output of this Ruby code using the pipeline operator?

def add_one(x)
  x + 1
end

def square(x)
  x * x
end

result = 3 |> add_one |> square
puts result

hard

A. 16

B. 10

C. 7

D. 9

Solution

1. Step 1: Apply the first pipeline operation

   The value 3 is passed to add_one, so add_one(3) returns 4.

2. Step 2: Apply the second pipeline operation

   The result 4 is then passed to square, so square(4) returns 16.

3. Final Answer:

   16 -> Option A

4. Quick Check:

   3 |> add_one |> square = 16 [OK]

Hint: Pipeline chains: left to right, each result feeds next method [OK]

Common Mistakes:

• Calculating square before add_one
• Adding 1 after squaring
• Confusing order of operations