These are the slides for an "Introduction to Elixir" presentation that was given at Lab Zero in San Francisco in October of 2016.

1. Lab Zero Innovations Inc.
77 Battery Street
San Francisco, CA 94111
415.839.6861
info@labzero.com
labzero.com
Introduction to Elixir
Brien Wankel
Sasha Voynow

3. What is Elixir?
Elixir is a dynamic, functional language designed for building scalable and
maintainable applications.
Elixir leverages the Erlang VM, known for running low-latency, distributed
and fault-tolerant systems, while also being successfully used in web
development and the embedded software domain.
● First release: 2012
● 1.0 in September 2014
● Takes advantage of the Erlang VM
○ Compiled to Erlang (BEAM) bytecode
○ Runs on the Erlang (BEAM) VM

4. Wait, did you say Erlang?
● Created in 1986 by Ericsson for telco exchange software
● Open Source since 1988
● A VM (BEAM)
● A set of libraries and tools (OTP)
● Engineered for
○ Fault tolerance (uptime!)
○ Responsiveness (low latency!)
○ Distributed computing (clustering! concurrency!)

5. Open Telecom Platform (OTP)
Search YouTube for: “Erlang: The Movie”

6. OTP
● a set of tools and libraries for implementing fault tolerant server
applications
● Some OTP jargon
○ Process: An extremely lightweight unit of execution
○ Application: A tree/graph of processes that are managed
together.
○ Project: What is normally thought of as an application. A
number of applications started together in the same VM

8. OSS in Erlang
Erlang in Production

9. If Erlang is so great, why Elixir?
Erlang has some UX issues
○ Funky, unfamiliar syntax
○ Lots of boilerplate
% module_name.erl
-module(module_name). % you may use some other name
-compile(export_all).
hello() ->
io:format("~s~n", ["Hello world!"]).
# module_name.ex
defmodule ModuleName do
def hello do
IO.puts "Hello World"
end
end

10. Elixir in Production

11. Types

12. The Usual Suspects
● Value Types
○ Int
○ Float
○ Atom :yo
○ String / Binary

13. ● Container Types
○ Tuple {1, :foo}
○ List [1,2,3]
○ Map %{foo: 10, bar: "baz" “foo” => “figgle”}
○ Struct
■ a named or tagged Map
■ %User{name: "Brien Wankel", company: "Lab Zero"}
● and some misc others

14. Pattern
M
atching

15. The Match Operator (=)
iex(1)> 3 = 3
3
iex(2)> x = 3
3
iex(3)> 3 = x
3
iex(4)> 2 = x
** (MatchError) no match of right hand side value: 3

16. The Pin Operator (^)
iex(1)> x = 3
3
iex(2)> y = x
3
iex(3)> x = 10
10
iex(4)> y
3
iex(5)> ^x = 3
** (MatchError) no match of right hand side value: 3
iex(5)> ^x = 10
10

17. Matching Lists
iex(1)> [a,b,c] = [1,2,3]
[1, 2, 3]
iex(2)> a
1
iex(3)> b
2
iex(4)> c
3
iex(1)> [h | t] = [1,2,3]
[1, 2, 3]
iex(2)> h
1
iex(3)> t
[2, 3]

18. Matching Maps
iex(1)> user = %{name: "Brien", status: :expired, state: "AZ"}
%{name: "Brien", state: "AZ", status: :expired}
iex(2)> %{name: theName} = user
%{name: "Brien", state: "AZ", status: :expired}
iex(3)> theName
"Brien"
iex(4)> %{name: theName, state: "CA"} = user
** (MatchError) no match of right hand side value: %{name:
"Brien", state: "AZ", status: :expired}

19. Matching in case statements
def registered_users do
case load_users_from_database() do
{:ok, users} -> users
{:err, error}
-> IO.puts("something went wrong: #{error}")
[]
end
end
def charge_user(user) do
case user do
%User{account_type: :premium} -> charge_card(user)
_ -> nil
end
end

20. Functions
# different functions
# &Lunchdown.string_to_int/1
def string_to_int(x) do
# ...
end
# &Lunchdown.string_to_int/2
def string_to_int(x, radix) do
# ...
end
# multiple heads of the same function
# &Lunchdown.find/1
def find([_h | _t] = ids) do
# ...
end
def find(id) do
# ...
end

21. Matching in Function Definitions
def handle_cast(:increment, state) do
{:noreply, state + 1}
end
def handle_cast(:decrement, state) do
{:noreply, state - 1}
end
def charge_credit_card(user = %User{account_type: :premium}) do
# charge the credit card
end
def charge_credit_card(_) do
# no-op
end

22. Matching in Function Definitions
# recursion
def sum([]), do: 0
def sum*([h | t]) do
h + sum(t)
end

23. Guard clauses
* You can only use a subset of built-in functions and operators
def charge_credit_card(cc_number, amount) when amount < 0, do: end
def charge_credit_card(cc_number, amount) do
# do some stuff
end

24. Pipelines and the |> operator
● A common elixir idiom for composing functions
● Building up complex transformations of data out of simpler ones in a way
that is readable and intention revealing
● APIs are commonly designed to work well with pipelines

25. Pipelines
def user_by_uid(uid) do
Authorization
|> where([a], a.uid == ^uid)
|> join(:inner, [a], u in User, u.id == a.user_id)
|> preload(:user)
|> Repo.one
end
def word_count(filename) do
increment = fn x -> x + 1 end
count_fun = fn w, m -> Map.update(m, w, 1, increment) end
filename
|> File.stream!
|> Stream.map(&String.trim/1)
|> Stream.flat_map(&String.split/1)
|> Stream.map(&String.downcase/1)
|> Enum.reduce(%{}, count_fun)
end

26. Modules
● The unit of code organization in Elixir
● Just a group of related functions.
defmodule Stack do
defstruct [:items]
# this defines a struct %Stack with the field items
def init do
%Stack{items: []}
end
def push(%Stack(items: items}, item), do: %Stack{items: items ++ [item]}
def pop(%Stack{items: [h | t]}), do: {:ok, h, %Stack{items: t}}
def pop(%Stack{items: []}), do: {:err, "no items"}
end

27. Elixir Ecosystem Highlights
● mix / hex
● Phoenix Framework
● ecto
● nerves
● distillery / edeliver

28. Further info
● elixir-lang.org
● hex.pm
● phoenix-framework.org
● Elixir Sips
● Google: “awesome elixir”
● elixirstatus.com

29. Thank you
info@labzero.com