Using Enum and Stream for Collection Processing Elixir

What You’ll Learn 📚

• Understanding the core concepts of Enum and Stream
• Key terminology and definitions
• Simple to complex examples with explanations
• Common questions and answers
• Troubleshooting common issues

Introduction to Enum and Stream

In Elixir, Enum and Stream are modules that provide a wide range of functions to work with collections like lists, maps, and ranges. They help you process data efficiently and elegantly. But what’s the difference between them?

Think of Enum as a toolbox for immediate collection processing, while Stream is like a conveyor belt that processes data lazily, only when needed.

Key Terminology

• Enum: A module for working with collections eagerly, meaning all operations are executed immediately.
• Stream: A module for lazy operations, where data is processed only when required.
• Lazy Evaluation: A technique where computation is deferred until the result is needed, improving efficiency.

Getting Started with Enum

The Simplest Example

# Using Enum to sum a list of numbers
numbers = [1, 2, 3, 4, 5]
sum = Enum.sum(numbers)
IO.puts("The sum is: #{sum}")

Progressively Complex Examples

Example 1: Filtering Even Numbers

# Filtering even numbers from a list
numbers = [1, 2, 3, 4, 5, 6]
even_numbers = Enum.filter(numbers, fn x -> rem(x, 2) == 0 end)
IO.inspect(even_numbers)

Example 2: Mapping Values

# Doubling each number in the list
numbers = [1, 2, 3, 4, 5]
doubled = Enum.map(numbers, fn x -> x * 2 end)
IO.inspect(doubled)

Example 3: Combining Operations

# Filtering and then mapping
numbers = [1, 2, 3, 4, 5, 6]
even_doubled = numbers |> Enum.filter(fn x -> rem(x, 2) == 0 end) |> Enum.map(fn x -> x * 2 end)
IO.inspect(even_doubled)

Introduction to Stream

Now, let’s explore Stream for lazy evaluation. It’s perfect for handling large datasets efficiently.

Example: Creating a Stream

# Creating a stream and processing it lazily
stream = 1..10 |> Stream.map(fn x -> x * 2 end)
IO.inspect(Enum.to_list(stream))

Common Questions and Answers

1. What’s the main difference between Enum and Stream?

   Enum processes collections eagerly, while Stream processes them lazily.

2. When should I use Stream over Enum?

   Use Stream for large datasets or when you want to defer computation until necessary.

3. Can I use Enum and Stream together?

   Yes, you can use them together by converting streams to lists or other collections.

4. Why is lazy evaluation beneficial?

   It saves memory and processing time by computing only what’s needed.

5. How do I troubleshoot errors with Enum or Stream?

   Check function names, arity, and ensure you’re using the correct module for your needs.

Troubleshooting Common Issues

If you encounter a function clause error, ensure you’re passing the correct arguments to Enum or Stream functions.

Remember, Enum functions return immediate results, while Stream functions return a stream that needs further processing.

Practice Exercises

• Create a list of numbers and use Enum to find the maximum value.
• Use Stream to generate an infinite series of numbers and take the first 10.
• Combine Enum and Stream to filter and transform a large dataset.

Keep practicing, and soon you’ll master collection processing in Elixir! 🎉

Additional Resources

• Elixir Enum Documentation
• Elixir Stream Documentation