Elixir Droplets: Pure Functions
A Contrast with Ruby and PHP
When exploring Elixir, a language deeply rooted in functional programming, you'll frequently encounter the concept of "pure functions." This concept is pivotal in understanding the Elixir way of coding, especially in languages like Ruby or PHP, where functions can have side effects. Let's explore what pure functions are and how they differ in these languages.
What are Pure Functions?
A pure function is a function where the return value is only determined by its input values without observable side effects. Given the same input, a pure function will always return the same output and do nothing else besides computing this output.
Characteristics of Pure Functions:
Deterministic: The output is predictable based solely on the input values.
No Side Effects: The function doesn't alter external states (like global variables, I/O, or database).
Pure Functions in Elixir
Elixir, being a functional language, encourages the use of pure functions. This aligns with its immutable nature, enhancing reliability and maintainability.
Example in Elixir
defmodule Math do
def square(number), do: number * number
end
IO.puts Math.square(4) # Outputs: 16Here, Math.square/1 is a pure function. It doesn't change any external state and, for the same input, will always produce the same output.
Comparing with Ruby and PHP
In contrast, Ruby and PHP, being more imperative and object-oriented, don't inherently enforce the purity of functions.
Example in Ruby
@counter = 0
def increment_counter(value)
@counter += value
end
increment_counter(5) # Changes the state of @counterThis Ruby method increment_counter is not pure because it modifies the external state (@counter).
Example in PHP
$counter = 0;
function incrementCounter(&$counter, $value) {
$counter += $value;
}
incrementCounter($counter, 5); // Alters the external $counter variableSimilarly, the PHP function incrementCounter changes the state of the passed variable $counter, making it impure.
Benefits of Pure Functions
Easier Testing and Debugging: Since pure functions don't depend on and don't alter external state, they are easier to test and debug.
Referential Transparency: Any call to a pure function can be replaced with its return value without changing the program's behavior.
Concurrency: Pure functions are inherently thread-safe, which simplifies writing concurrent applications.
Transitioning to Pure Functions
For developers moving from Ruby or PHP to Elixir, embracing pure functions involves:
Avoiding functions that modify external state.
Not relying on data outside the function's scope, unless passed as an argument.
Ensuring functions don't produce side effects like writing to a database, modifying a file, etc.
Conclusion
Adopting pure functions in Elixir leads to more predictable, maintainable, and robust code. While this might require a shift in thinking for developers accustomed to Ruby or PHP, the clarity and simplicity it brings to your code are well worth the effort.
As you delve deeper into Elixir, the elegance and power of pure functions become increasingly apparent, influencing not just how you code, but how you think about solving problems programmatically.