Elixir Learning Part 1

Yo! It's time to start learning new languages. Elixir is a language that I started to learn. Below are few notes:

• Everything in Elixir is an expression that has a return value.

• Module is a collection of functions, something like a namespace. Every Elixir function must be defined inside a module.

  • To call a fucntion of a module, use the syntax : ModuleName.function_name(args)
  • To define your own module, use the defmodule contruct.
  • Inside the module, using def contruct to define function.

  • defmodule and def are compilation constructs called macros

      defmodule Geometry do
        def rectangle_area(a, b) do
          a * b
        end
      end
      

  • A module name must follow certain rules: start with an uppercase letter and is usually written in CamelCase style.

• Function must always be a part of a module. Function name start with lowercase letter and underscore character.

  • Function names can end with ? or !
    • ? means a function returns true of false
    • ! means a function may raise a runtime error
  • If a function has no arguments then we can omit parentheses.

• To combine functions, passing the result of one function as the argument to the next one. Elixir comes with a built-in operator: |> - pipeline operator

        iex(2)> -5 |> abs |> Kernel.+(6)
        11
    

• Arity is a fancy name for the number of arguments a funciton receives.

          defmodule Greeting do
            def say_hi(name) do
              # ...
            end
          end
    

  • The function Greeting.say_hi receives one argument so function arity is 1.
  • This function is often called Greeting.say_hi/1

• Two functions with the same name but different arities are two different functions.

          defmodule Geometry do
            def area(a, b) do # Arity: Geometry.area/2
              a * b
            end
    
            def area(a) do # Arity: Geometry.area/1
              area(a, a)
            end
          end
    
          # Geometry.area(5) # => 25
          # Geometry.area(3,4) # => 12
    

  • It usually make no sense for different functions with a same name to have completely different implementations.
  • In general, a lower-arity function delegates to a higher-arity function.

  • Elixir allows you to specify defaults for argument by using the \\ operator.

       defmodule Geometry do
         def sum(a, b \\ 0)
           a + b
         end
       end
       # Geometry.sum(5) # => 5
       # Geometry.sum(4,6) # => 10
      

• Using def macro when define a function, the function is made public. Using defp macro to make the function private.