Day10 - |> The pipe operator

04/12/20191 Min Read — In Elixir

So far I have mainly developed software using OOP languages like Java, Python or Scala. All these languages share some common OOP concepts such as classes for defining custom types, methods for encapsulation to ensure consistency, or inheritance and polymorphism for late binding. Elixir as a functional language, however, offers several different concepts. The 'building blocks' of an Elixir application are modules and functions, not classes and methods. An Elixir module can be imagined as a named collection of functions. In Elixir, you call a function by referring to its module as String.ends_with?("abc", "c"). By the way: Function names in Elixir are written in snake_case instead of camelCase for reasons of readability.

Unlike the OOP languages mentioned above, you can't call a function on an object directly in Elixir. This really differs from other languages, where you call a function by referring to an object like "abc".endsWith("c"). In Java or Scala it is the compiler's job to pass a reference to the corresponding object as the first argument, not so in Elixir! I have to admit that I found this module+function combination a bit strange when I first saw it. However, this brings big advantages as we will see in a moment - Ladies and gentlemen, please welcome the pipe operator!

The Pipe Operator

Maybe you've come across nested, hard to read function calls like this:

print(count(split(read_file("words.txt"), "\n")))

In my opinion, the code above has two major problems:

  1. The nesting makes it really hard to follow the code!
  2. The sequence of the function execution is in reverse order compared to the reading direction!

In order to avoid code like this, Elixir introduces the 'pipe' operator which is written as |>. The pipe operator takes the value on the left-hand side and uses it as the first argument to the function on the right-hand side:

|> read_file
|> split("\n")
|> count
|> print

Using the pipe operator makes the code much more readable by simply reading the transformation steps from top to bottom. Pretty nice 😎

Be curious about next week, I will present Elixir's pattern matching concepts.

See you then, cheers!