Elixir basics

elixir-basics.md

Elixir

Setup

Installation

$ brew update
$ brew install erlang
$ brew install elixir

Basic commands

# open editor (like IRB)
$ iex

# load file and editor
$ iex "path/to/filename.ex"

# start a new project
$ mix new project_name

# load all modules in project directory
$ iex -S mix

# load a file
iex> c “path/to/filename.ex”

# reload an elixir module
iex> r ModuleName

# get previous console output (underscore in rails console)
iex> v

Functional Paradigms - Matchers, Maps & More

Functions

iex> add1 = fn(x) -> x + 1 end
iex> add1 = &(&1+1)
iex> add1.(4)
5

iex> fun = fn(x) -> Kernel.is_atom(x) end
iex> fun = &Kernel.is_atom/1
iex> fun.(:atom)
true

Pipes

defmodule Handler do
  def handle(request) do
    conv = parse(request)
    conv = route(conv)
    format_response(conv)
  end

  # or
  def handle(request) do
    format_response(route(parse(request)))
  end

  # with pipes!
  def handle(request) do
    request
    |> parse
    |> route
    |> format_response
  end
end

Maps

defmodule User do
  defstruct name: "John Doe", age: nil
end

iex>
name
=> undefined
%{name: name} = %User{}
name
=> John Doe

Guards

defmodule User do
  defstruct name: "Jane Doe", age: 18

  def serve_drinks(%User{age: age, name: name}) when age >= 21 do
    IO.puts "Hello #{name}, you are over 21. Enjoy drinking!"
  end

  def serve_drinks(%User{age: age, name: name}) do
    IO.puts "Sorry #{name}, you are not over 21. No booze for you!"
  end
end

iex>
user = %User{}
=> %User{age: 18, name: "John Doe"}
User.serve_drinks(user)
=> Sorry John Doe, you are not over 21. No booze for you!

Lists

defmodule Loop do
  def over([head | tail]) do
    IO.puts "This is now the head: #{head}"
    over(tail)
  end

  def over([]) do
    IO.puts "List is empty now."
  end
end

iex>
list = [1,2,3]
Loop.over(list)
=>
This is now the head: 1
This is now the head: 2
This is now the head: 3
List is empty now.
:ok

Pattern matching

iex> {:ok, result} = {:ok, 13}
{:ok, 13}
iex> result
13

iex> {:ok, result} = {:error, :oops}
** (MatchError) no match of right hand side value: {:error, :oops}

Processes & Messaging

current_process = self()

# Spawn an Elixir process (not an operating system one!)
spawn_link(fn ->
  send current_process, {:msg, "hello world"}
end)

# Accessing messages in processor mailbox
iex> Process.info(current_process, :messages)
=> {:messages, [msg: "hello world"]}

# Block until the message is received
receive do
  {:msg, contents} -> IO.puts contents
end

PID

pid = self()
#PID<0.317.0>

string = "#PID<0.317.0>"

string
  |> :erlang.binary_to_list
  |> :erlang.list_to_pid

https://elixir-examples.github.io/examples/elixir-and-ruby-comparison