Covers: Ruby, Io, Prolog, Scala, Erlang, Clojure, Haskell

Basic Types

iex> my_utf8_string = "hello Iñtërnâtiônàlizætiøn"
"hello Iñtërnâtiônàlizætiøn"
­
iex> my_atom = :hello
:hello
­
iex> 1000 == 1_000
true
­
iex> 0.314159e1 == 314159.0e-5
true
­
iex> my_range = 1..5
1..5

Tuples, Lists, Maps

iex> my_tuple = {:ok, "return value", 715}
{:ok, "return value", 715}
­
iex> my_list = [1, 2, 3, 4, 5]
[1, 2, 3, 4, 5]
­
iex> my_map = %{:first => "Ted", :last => "Naleid"}
%{first: "Ted", last: "Naleid"}

Closures

iex> sum = fn a, b -> a + b end
#Function<12.90072148/2 in :erl_eval.expr/5>
­
iex> sum.(1, 2)
3
­
# shortened closure syntax:
­
iex> short_sum = &(&1 + &2)
&:erlang.+/2
­
iex> short_sum.(1, 2)
3

Structs

iex> defmodule Person do
...>   defstruct first: "Ted", last: "Naleid"
...> end
{:module, Person, …}
­
iex> %Person{}
%Person{first: "Ted", last: "Naleid"}
­
iex> %Person{first: "Hazel"}
%Person{first: "Hazel", last: "Naleid"}
­
iex> %Person{nope: "Bad Field"}
** (CompileError) iex:4: unknown key :nope for struct

Protocols

iex> defprotocol Stringable do
...>   def to_string(value)
...> end
­
iex> defimpl Stringable, for: Person do
...>   def to_string(value) do
...>     "#{value.first} #{value.last}"
...>   end
...> end
­
iex> Stringable.to_string(%Person{})
"Ted Naleid"

Some similarities to an OOP Interface

Pattern Matching

iex> a = {:ok, 1}
{:ok, 1}  
­
iex> {:ok, b} = {:ok, 1}
{:ok, 1}
­
iex> b
1    

Pattern Matching Lists

iex> [a, b, c] = [1, 2, 3]
[1, 2, 3]
­
iex> a
1
­
iex> [head | tail] = [1, 2, 3]
[1, 2, 3]
­
iex> head
1
­
iex> tail
[2, 3]

Pattern Matching Structs

case HTTP.get(url) do
  {:ok, %HTTP.Resp{ status: 200, body: body }} ->
    IO.puts body
  {:ok, %HTTP.Resp{ status: 404 }} ->
    IO.puts "Not found :("
  {:ok, %HTTP.Resp{ status: status }} ->
    IO.puts "HTTP Status: #{status}"
  {:error, %HTTP.Error{ reason: reason }} ->
    IO.inspect reason
  _ ->
    IO.puts "¯\_(ツ)_/¯"
end     

Even More Pattern Matching

def execute({:ok, good_value}) do
  IO.puts "Known good value: #{good_value}"
end
­
def execute({:error, error_reason}) do
  IO.puts "Error! #{error_reason}"
end
­
iex> execute({:ok, "Yay!"})
Known good value: Yay!
­
iex> execute({:error, "Boo!"})
Error! Boo!

Pipe Operator |>

defmodule Shop do
  defp apply_tax(prices) do 
    Enum.map(prices, fn v -> v * 1.1 end)
  end
­
  def cart_total(items) do
    Enum.sum(
      apply_tax(
        Enum.map(items, fn item -> item.price end)))
  end
end 
­
Shop.cart_total([%{:price=>5.00}, %{:price=>2.00}])
# => 7.7

Nested cart_total is hard to read, have to read inside out

Pipe Operator |>

  def cart_total(items) do
    prices = Enum.map(items, fn itm -> itm.price end)
    prices_with_tax = apply_tax(prices)
    Enum.sum(prices_with_tax)
  end

Intermediate variables cleans up a bit

Pipe Operator |>

def cart_total(items) do
  items
  |> Enum.map(fn item -> item.price end)
  |> add_tax
  |> Enum.sum
end

|> operator passes result from last method as first param in next

Similar to unix pipe: ps ax | grep iex | awk '{ print $1 }'

Debugging via pry

require IEx
­
def index(conn, _params) do
  IEx.pry
  conn |> render "index"
end

Similar to the JavaScript debugger; command

Erlang Activity Monitor

iex> :observer.start

Easy Access to AST

iex> ast = quote, do 2 * 2 / 7
{:/,[context: Elixir, import: Kernel],
 [{:*,[context: Elixir, import: Kernel], [2, 2]}, 7]}

Underlying AST looks a bit like a lisp

Full discussion bigger than this presentation, check out "Metaprogramming Elixir", by Chris McCord

WhatsApp Runs On Erlang VM

• 465M monthly users
• 19B messages in & 40B out per day
• 600M pictures, 200M voice, 100M videos
• 147M peak concurrent connections
• 230k peak logins/second
• 342K peak msgs in/sec, 712K out

At time of Facebook acquisition for $19 Billion

hex.pm on Single 512MB Heroku Dyno

(~0.15 load, from https://twitter.com/emjii/status/591240463782391808)

Concurrency Built-in

iex> parent = self()
#PID<0.90.0>
­
iex> spawn(fn -> send parent, "hello world" end)
#PID<0.93.0>
­
iex> receive do message -> IO.puts message end
hello world
:ok

Great, Growing Community

Hex Downloads (from @emjii on 2015-06-24)