The document introduces Elixir and discusses its origins and key features. It notes that Elixir was created by José Valim as a functional programming language that provides better concurrency, scalability and fault tolerance compared to Ruby on Rails. It was influenced by and borrows features from Erlang, including immutability, concurrency, distribution and fault tolerance. Some of Elixir's key features that enable these properties are discussed such as processes, the actor model, supervision trees, and immutable, function-based programming.

1. ELIXIR
LEARNING DAY

2. INTRO TO ELIXIR
WHY ELIXIR?
▸ Rails core dev José Valim found problems in Rails which
could not be solved by Ruby.
▸ Scalability, concurrency, real-time communication
▸ Looked for other languages that provided it.
▸ Didn’t find one that had both a nice syntax (developer
happiness) and solved the problems features.
▸ He did find Erlang.

3. ERLANG
ERLANG FEATURES
▸ Created in the 80s by Ericsson, to
support telephony systems.
▸ Scalable, consumes all cores, fault
tolerant, functional programming
▸ When was the last time your cell phone
network went down to apply an
update? Hot code swapping.
▸ Fault tolerant. Let it fail! Restart a
process when it fails. Supervisor
processes watch other processes. Kill
and restart failing processes.
▸ WhatsApp: 900 million users, 50
engineers

4. ERLANG FEATURES
FUNCTIONAL PROGRAMMING
▸ “Functional” refers to a mathematical function: given
certain inputs, it will always return the same output.
▸ Functions are first-class citizens.
▸ State is immutable.
▸ Lends itself to concurrent programming.
▸ More cores.

5. %% Loop uses a list for times in order to go around
%% the ~49 days limit on timeouts.
loop(S = #state{server=Server, to_go=[T|Next]}) ->
receive
{Server, Ref, cancel} ->
Server ! {Ref, ok}
after T*1000 ->
if Next =:= [] ->
Server ! {done, S#state.name};
Next =/= [] ->
loop(S#state{to_go=Next})
end
end.
ERLANG SYNTAX…

6. THE BEST OF BOTH WORLDS
}

7. $ iex
Erlang/OTP 18 [erts-7.1] [source] [64-bit]
[smp:8:8] [async-threads:10] [hipe] [kernel-
poll:false] [dtrace]
Interactive Elixir (1.1.1) - press Ctrl+C to
exit (type h() ENTER for help)
iex(1)> 1+1
2
iex(2)>
REPL

8. x = [1, 2]
// Ruby
x.push(3)
=> [1, 2, 3]
x.push(4)
=> [1, 2, 3, 4]
// Elixir
List.insert_at(x, -1, 3)
=> [1, 2, 3]
List.insert_at(x, -1, 4)
=> [1, 2, 4]
IMMUTABLE STATE

9. add = fn num1, num2 ->
num1 + num2
end
subtract = fn num1, num2 ->
num1 - num2
end
calculate = fn num1, num2, operation ->
operation.(num1, num2)
end
calculate.(17, 4, add)
calculate.(17, 4, subtract)
FUNCTIONS: FIRST-CLASS CITIZENS

10. defmodule Convert do
def kph_to_mph(kph) do
kph/1.60934
end
def mph_to_mps(mph) do
mph / 2.23693629
end
end
Convert.kph_to_mph(100)
=> 62.137273664980675
MODULES

11. mph = Convert.kph_to_mph(100)
=> 62.137273664980675
Convert.mph_to_mps(mph)
=> 27.777846844704136
Convert.kph_to_mph(100) |> Convert.mph_to_mps
=> 27.777846844704136
PIPE OPERATOR

12. defmodule Calculator do
def sqrt(x) do
:math.sqrt(x)
end
end
Calculator.sqrt(-1)
** (ArithmeticError) bad argument in
arithmetic expression
(stdlib) :math.sqrt(-1)
iex:47: Calculator.sqrt/1
FUNCTION GUARDS (1)

13. defmodule Calculator do
def sqrt(x) when x >= 0 do
:math.sqrt(x)
end
end
Calculator.sqrt(-1)
** (FunctionClauseError) no function clause
matching in Calculator.sqrt/1
iex:47: Calculator.sqrt(-1)
FUNCTION GUARDS (2)

14. defmodule Calculator do
def add(x, y) do
x + y
end
def add(x, y, z) do
x + y + z
end
end
Calculator.add(1, 2)
=> 3
Calculator.add(1, 2, 3)
=> 6
FUNCTION OVERLOADING

15. [x, y] = [1, 2]
=> [1, 2]
x
=> 1
y
=> 2
PATTERN MATCHING (1)

16. defmodule GPS do
def location_name(lat, long) do
# lots of processing here
%{city: "Santiago", country: "Chile"}
end
end
%{city: mycity} = GPS.location_name(0.1, 0.2)
=> %{city: "Santiago", country: "Chile"}
mycity
=> "Santiago"
PATTERN MATCHING (2)

17. defmodule Factorial do
def fact(0), do: 1
def fact(n) do
n*fact(n-1)
end
end
Factorial.fact(0)
=> 1
Factorial.fact(1)
=> 1
Factorial.fact(4)
=> 24
PATTERN MATCHING (3)

18. defmodule Factorial do
@moduledoc """
Contains a bunch of functions to calculate factorials
"""
@doc """
Calculates the factorial of the given number
"""
def fact(0) do
1
end
def fact(num) do
num * fact(num-1)
end
end
INLINE DOCUMENTATION (1)

19. h Factorial
=>
Factorial
Contains a bunch of functions to calculate
factorials
h Factorial.fact
=>
def fact(num)
Calculates the factorial of the given
number
INLINE DOCUMENTATION (2)

20. MOTIVATION
AKA ELIXIR ON RAILS

21. MOTIVATION
PHOENIX PERFOMANCE
Source: https://github.com/mroth/phoenix-showdown