Programming Elixir ≥ 1.6

Coding with Immutable Data

Once you accept the concept, coding with immutable data is surprisingly easy. You just have to remember that any function that transforms data will return a new copy of it. Thus, we never capitalize a string. Instead, we return a capitalized copy of a string.

iex> name = "elixir"
"elixir"
iex> cap_name = String.capitalize name
"Elixir"
iex> name
"elixir"

If you’re coming from an object-oriented language, you may dislike that we write String.capitalize name and not name.capitalize(). But in object-oriented languages, objects mostly have mutable state. When you make a call such as name.capitalize() you have no immediate indication whether you are changing the internal representation of the name, returning ...