Defining and Calling Functions in Elixir

What You’ll Learn 📚

• Understanding what functions are and why they’re important
• How to define and call functions in Elixir
• Common mistakes and how to avoid them
• Practical examples to solidify your understanding

Introduction to Functions

In programming, a function is a reusable block of code that performs a specific task. Functions help us avoid repetition and make our code more organized and readable. In Elixir, functions are first-class citizens, meaning they can be passed around just like any other value.

Key Terminology

• Function Definition: The code that specifies what a function does.
• Function Call: The code that executes the function.
• Parameters: Inputs to the function.
• Return Value: The output of the function.

Let’s Start with a Simple Example 🐣

defmodule Math do  # Define a module named Math
  def add(a, b) do # Define a function named add
    a + b         # Return the sum of a and b
  end
end

IO.puts Math.add(2, 3) # Call the add function with 2 and 3

Progressively Complex Examples 🚀

Example 1: Function with Multiple Clauses

defmodule Greeter do
  def greet(:morning), do: "Good morning!"
  def greet(:evening), do: "Good evening!"
  def greet(_), do: "Hello!"
end

IO.puts Greeter.greet(:morning) # Outputs: Good morning!
IO.puts Greeter.greet(:evening) # Outputs: Good evening!
IO.puts Greeter.greet(:afternoon) # Outputs: Hello!

Example 2: Recursive Function

defmodule Factorial do
  def of(0), do: 1
  def of(n) when n > 0 do
    n * of(n - 1)
  end
end

IO.puts Factorial.of(5) # Outputs: 120

Example 3: Anonymous Functions

add = fn a, b -> a + b end

IO.puts add.(5, 7) # Outputs: 12

Common Questions and Answers 🤔

1. What is a function in Elixir?

   A function is a reusable block of code that performs a specific task. In Elixir, functions can be defined within modules and can have multiple clauses to handle different cases.

2. How do I define a function in Elixir?

   Use the def keyword within a module to define a function. Specify the function name, parameters, and the code block that performs the task.

3. What are anonymous functions?

   Anonymous functions are functions that are not bound to a name. They are defined using the fn keyword and are often used for short-lived tasks.

4. How do I call a function in Elixir?

   Use the module name followed by a dot and the function name, passing any required arguments. For example, Math.add(2, 3).

5. What is a recursive function?

   A recursive function is a function that calls itself to solve a problem. It’s often used for tasks that can be broken down into similar sub-tasks.

Troubleshooting Common Issues 🛠️

If you see an error like undefined function, make sure your function is defined within a module and you’re calling it correctly.

Remember, Elixir is case-sensitive! add and Add are not the same.

Practice Exercises 🏋️

• Create a module Calculator with functions for subtraction, multiplication, and division.
• Write a recursive function to calculate the nth Fibonacci number.
• Experiment with anonymous functions by creating one that squares a number.

Additional Resources 📚

• Elixir Official Documentation
• Elixir School: Functions

Keep practicing, and remember, every expert was once a beginner. You’ve got this! 💪