Learn Functional Programming with Elixir

Working with Immutable Data

Conventional languages use mutating shared values that require thread and lock mechanisms to work with concurrency and parallelism. In functional programming, all values you create in your program are immutable. By default, each function will have a stable value. That means we don’t need lock mechanisms, which simplifies the parallel work. It changes everything about building software.

Look at this Elixir code:

list = [1, 2, 3, 4]
List.delete_at(list, -1)
# => [4]

list ++ [1]
# => [1, 2, 3, 4, 1]

IO.inspect list
# => [1, 2, 3, 4]

The value of list is immutable: no matter the operation we apply to it, it will generate new values. If the list is immutable and each operation has a safe value, the compiler ...