Lazy enumerators in Ruby - Mini Project: Build & Apply

Lazy Enumerators in Ruby

📖 Scenario: Imagine you have a long list of numbers, but you want to process them one by one without loading all at once. This is useful when working with big data or streams.

🎯 Goal: You will create a lazy enumerator to filter and transform numbers efficiently, then print the first few results.

📋 What You'll Learn

Create an array of numbers from 1 to 1000

Create a lazy enumerator from the array

Use lazy methods to select even numbers and multiply them by 3

Print the first 5 results from the lazy enumerator

💡 Why This Matters

🌍 Real World

Lazy enumerators help process large or infinite data streams without using too much memory, like reading big files or handling live data feeds.

💼 Career

Understanding lazy enumerators is useful for Ruby developers working on performance-critical applications, data processing, and backend services.

1

Create an array of numbers

Create an array called numbers containing numbers from 1 to 1000.

Ruby

# Create an array called numbers with values from 1 to 1000
# Your code here

Need a hint?

Use a range from 1 to 1000 and convert it to an array with to_a.

2

Create a lazy enumerator

Create a lazy enumerator called lazy_numbers from the numbers array using the lazy method.

Ruby

numbers = (1..1000).to_a
# Create a lazy enumerator called lazy_numbers from numbers
# Your code here

Need a hint?

Call lazy on the numbers array to create a lazy enumerator.

3

Filter and transform lazily

Use the lazy_numbers enumerator to select even numbers with select and multiply each by 3 with map. Store the result in processed_numbers.

Ruby

numbers = (1..1000).to_a
lazy_numbers = numbers.lazy
# Use select to keep even numbers and map to multiply by 3, assign to processed_numbers
# Your code here

Need a hint?

Chain select and map on lazy_numbers to filter and transform lazily.

4

Print the first 5 results

Print the first 5 elements of processed_numbers using the first method.

Ruby

numbers = (1..1000).to_a
lazy_numbers = numbers.lazy
processed_numbers = lazy_numbers.select { |n| n.even? }.map { |n| n * 3 }
# Print the first 5 elements of processed_numbers
# Your code here

Need a hint?

Use first(5) to get the first five elements and puts to print them.