How Elixir is Transforming My Mind

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How Elixir is Transforming my Mind @nicholasjhenry, #myelixirstatus 12

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Functional Programming approaches the mainstream 1 » composability » modularity » equational reasoning » parallelism 1 https://www.quora.com/What-advantages-do-functional-programming-languages-introduce @nicholasjhenry, #myelixirstatus 2

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Becoming aware of these FP languages » Haskell » Scala » Elm » Clojure » and more... @nicholasjhenry, #myelixirstatus 3

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So I started to explore... @nicholasjhenry, #myelixirstatus 4

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@nicholasjhenry, #myelixirstatus 5

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@nicholasjhenry, #myelixirstatus 6

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@nicholasjhenry, #myelixirstatus 7

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@nicholasjhenry, #myelixirstatus 8

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@nicholasjhenry, #myelixirstatus 9

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But nothing seemed to stick @nicholasjhenry, #myelixirstatus 10

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Meet Elixir » a screencast original published by PeepCode (now on Pluralsight) » presented by José Valim (created of Elixir) » parse the meta-data for a collection of video streaming files » and that was the first day a transformation began @nicholasjhenry, #myelixirstatus 11

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How Elixir is Transforming my Mind @nicholasjhenry, #myelixirstatus 12

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This is not an overview of Elixir (or an introduction to Functional Programming) @nicholasjhenry, #myelixirstatus 13

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These are the features that make Elixir fun for me (And I hope fun for you too) @nicholasjhenry, #myelixirstatus 14

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Five things you need to know 1. Elixir runs on the Erlang VM 2. Functional Programming Language 3. Created by José Valim 4. It's not "Ruby on the Erlang VM" 5. Yes, there is a web framework - Phoenix @nicholasjhenry, #myelixirstatus 15

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How Elixir has tranformed how I: 1. dispatch behaviour 2. work with data 3. think about concurrency @nicholasjhenry, #myelixirstatus 16

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#myelixirstatus I have: » not deployed a production application » read way to many books » attended ElixirConf this year in Austin, Texas @nicholasjhenry, #myelixirstatus 17

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1. How Elixir has transformed how I dispatch behaviour @nicholasjhenry, #myelixirstatus 18

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how we dynamically choose behavior within our program -- Neal Ford, Functional Thinking @nicholasjhenry, #myelixirstatus 19

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Before: leverage if statements to dynamically choose behaviour @nicholasjhenry, #myelixirstatus 20

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Now: leverage pattern matching to dynamically choose behaviour @nicholasjhenry, #myelixirstatus 21

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Example: Refactoring from testing conditions to matching patterns Deﬁne a function that creates a new customer: * name cannot be blank. * state cannot be blank. * domain cannot be blank. * enabled must be true to start with. @nicholasjhenry, #myelixirstatus 22

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// original example if(name.isEmpty) { println("Name cannot be blank") null } else if(state.isEmpty) { println("State cannot be blank") null } else if(domain.isEmpty) { println("Domain cannot be blank") null } else { new Customer( 0, name, state, domain, true ) } @nicholasjhenry, #myelixirstatus 23

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iex> Customer.create("Nicholas", "Québec", "ﬁrsthand.ca") %Customer{domain: "ﬁrsthand.ca", name: "Nicholas", state: "Québec"} @nicholasjhenry, #myelixirstatus 24

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# poorly translated example defmodule Customer do defstruct name: nil, state: nil, domain: nil, enabled: true # %Customer{name: name, state: state, domain: domain} end @nicholasjhenry, #myelixirstatus 25

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# poorly translated example defmodule Customer do defstruct name: nil, state: nil, domain: nil, enabled: true def create(name, state, domain) do end end @nicholasjhenry, #myelixirstatus 26

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# poorly translated example defmodule Customer do defstruct name: nil, state: nil, domain: nil, enabled: true def create(name, state, domain) do if name == "" do IO.puts "Name cannot be blank" else if state == "" do IO.puts "State cannot be blank" else if domain == "" do IO.puts "Domain cannot be blank" else %Customer{name: name, state: state, domain: domain} end end end end end @nicholasjhenry, #myelixirstatus 27

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Challenge » move from imperative implementation » we describing each step of the function » towards declarative implementation » we describe what we want @nicholasjhenry, #myelixirstatus 28

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Declarative Example » a declarative language we use every day: » results in more expressive programs SELECT * FROM CUSTOMERS; @nicholasjhenry, #myelixirstatus 29

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How? Pattern Matching » not regular expressions /hay/.match('haystack') #=> # » match scalar and non-scalar types » demonstrates why Elixir is not Ruby on the Erlang VM @nicholasjhenry, #myelixirstatus 30

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= is not assignment iex> a = 10 iex> 10 = a irb> a = 10 => 10 irb> 10 = a SyntaxError: (irb):2: syntax error, unexpected '=', expecting end-of-input 10 = a ^ @nicholasjhenry, #myelixirstatus 31

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= is a match operator iex> a = 10 iex> 20 = a ** (MatchError) no match of right hand side value: 10 » left-hand-side: "pattern" » right-hand-side: "term" @nicholasjhenry, #myelixirstatus 32

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Pattern-matching on Tuples iex> {a, b, c} = {:hello, "world", 42} {:hello, "world", 42} @nicholasjhenry, #myelixirstatus 33

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Pattern-matching on Tuples iex> {a, b, c} = {:hello, "world", 42} {:hello, "world", 42} iex> a :hello @nicholasjhenry, #myelixirstatus 34

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Pattern-matching on Tuples iex> {a, b, c} = {:hello, "world", 42} {:hello, "world", 42} iex> a :hello iex> b "world" @nicholasjhenry, #myelixirstatus 35

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Pattern-matching on Tuples iex> {a, b, c} = {:hello, "world", 42} {:hello, "world", 42} iex> a :hello iex> b "world" iex> c 42 @nicholasjhenry, #myelixirstatus 36

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Mis-match Pattern iex> {:hello, b, c} = {:hello, "world", 42} {:hello, "world", 42} @nicholasjhenry, #myelixirstatus 37

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Mis-match Pattern iex> {:hello, b, c} = {:hello, "world", 42} {:hello, "world", 42} iex> {:gidday, b, c} = {:hello, "world", 42} ** (MatchError) no match of right hand side value: {:hello, "world", 42} @nicholasjhenry, #myelixirstatus 38

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Pattern matching used everywhere » binding values to variables (just demonstrated) » conditions and loops (coming-up) » function declarations and invocation (coming-up) » recursion (not covered today) @nicholasjhenry, #myelixirstatus 39

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defmodule Customer do defstruct name: nil, state: nil, domain: nil, enabled: true def create(name, state, domain) do if name == "" do IO.puts "Name cannot be blank" else if state == "" do IO.puts "State cannot be blank" else if domain == "" do IO.puts "Domain cannot be blank" else %Customer{name: name, state: state, domain: domain} end end end end end @nicholasjhenry, #myelixirstatus 40

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# use pattern matching with a case statement defmodule Customer do defstruct name: nil, state: nil, domain: nil, enabled: true def create(name, state, domain) do # case :term case {name, state, domain} do # clause (:head -> :body) {"", _state, _domain} -> IO.puts "Name cannot be blank" end end end @nicholasjhenry, #myelixirstatus 42

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# use pattern matching with a case statement defmodule Customer do defstruct name: nil, state: nil, domain: nil, enabled: true def create(name, state, domain) do case {name, state, domain} do {"", _state, _domain} -> IO.puts "Name cannot be blank" {_name, "", _domain} -> IO.puts "State cannot be blank" end end end @nicholasjhenry, #myelixirstatus 43

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# use multi-clause functions defmodule Customer do defstruct name: nil, state: nil, domain: nil, enabled: true # multi-clause functions coming here soon end @nicholasjhenry, #myelixirstatus 46

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# use multi-clause functions defmodule Customer do defstruct name: nil, state: nil, domain: nil, enabled: true def create("", _state, _domain), do: IO.puts "Name cannot be blank" def create(_name, "", _domain), do: IO.puts "State cannot be blank" def create(_name, _state, ""), do: IO.puts "Domain cannot be blank" end @nicholasjhenry, #myelixirstatus 48

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So, how has Elixir transformed how I dispatch behaviour? @nicholasjhenry, #myelixirstatus 50

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Dispatching Behaviour Pattern matching in Elixir (and FP languages in general) moves me away from an imperative approach, towards a more declarative approach, producing more expressive code. @nicholasjhenry, #myelixirstatus 51

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2. How Elixir has transformed how I work with data @nicholasjhenry, #myelixirstatus 52

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Before Encapsulate data (state) within an object and mutate that data via method calls @nicholasjhenry, #myelixirstatus 53

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Now Transform data with a pipeline of functions @nicholasjhenry, #myelixirstatus 54

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We transform data all the time » HTTP request to an HTTP Response » SQL query to collection of objects » a CSV document to hash @nicholasjhenry, #myelixirstatus 55

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Example: Count words iex> expected = %{ "one" => 1 , "fish" => 4 , "two" => 1 , "red" => 1 , "blue" => 1 } iex> Words.count("one fish two fish red fish blue fish") == expected true @nicholasjhenry, #myelixirstatus 56

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Requirements 1. Count multiple occurances 2. Ignore punctuation 3. Include numbers 4. Normalize case @nicholasjhenry, #myelixirstatus 57

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Sketch sentence |> Remove punctuation |> Normalize case |> Split into words |> Count words @nicholasjhenry, #myelixirstatus 58

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Temporary variables module Words def count(sentence) do sentence1 = remove_punctuation(sentence) sentence2 = normalize_case(sentence1) sentence3 = split_into_words(sentence2) count_words(sentence3) end # private functions deﬁned below end @nicholasjhenry, #myelixirstatus 59

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Staircasing module Words def count(sentence) do count_words( split_into_words( normalize_case( remove_punctuation(sentence) ) ) ) end # private functions deﬁned below end @nicholasjhenry, #myelixirstatus 60

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Challenge rewrite the function without: - temporary variables - staircasing @nicholasjhenry, #myelixirstatus 61

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Meet the pipe operator val |> my_function(a, b) same as: my_function(val, a, b) @nicholasjhenry, #myelixirstatus 62

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You have probably used pipes before ls | wc -l @nicholasjhenry, #myelixirstatus 63

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# refactored with the Pipe Operator module Words def count(sentence) do sentence end # private functions deﬁned below end @nicholasjhenry, #myelixirstatus 64

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# refactored with the Pipe Operator module Words def count(sentence) do sentence |> remove_punctuation end # private functions deﬁned below end @nicholasjhenry, #myelixirstatus 65

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# refactored with the Pipe Operator module Words def count(sentence) do sentence |> remove_punctuation |> normalize_case end # private functions deﬁned below end @nicholasjhenry, #myelixirstatus 66

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# refactored with the Pipe Operator module Words def count(sentence) do sentence |> remove_punctuation |> normalize_case |> split_into_words end # private functions deﬁned below end @nicholasjhenry, #myelixirstatus 67

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# refactored with the Pipe Operator module Words def count(sentence) do sentence |> remove_punctuation |> normalize_case |> split_into_words |> count_words end # private functions deﬁned below end @nicholasjhenry, #myelixirstatus 68

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So, how has Elixir transformed how I work with data? @nicholasjhenry, #myelixirstatus 69

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Programming is transforming data, and the |> operator makes that transformation explicit. -- Dave Thomas, Programming with Elixir @nicholasjhenry, #myelixirstatus 70

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3. How Elixir has transformed how I think about Concurrency @nicholasjhenry, #myelixirstatus 71

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Concurrency vs. Parallelism 10 » Concurrency: dealing with multiple things at once » Parallelism: doing multiple things at once 10 http://concur.rspace.googlecode.com/hg/talk/concur.html#slide-5 @nicholasjhenry, #myelixirstatus 72

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Before something to avoid @nicholasjhenry, #myelixirstatus 73

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Now I actually use it. I use it often. @nicholasjhenry, #myelixirstatus 74

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The Actor Model: a programming model for currency @nicholasjhenry, #myelixirstatus 75

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Understanding the Actor Model 1. Actor == independent process 2. Shares nothing with any other process 3. processes send and receive messages @nicholasjhenry, #myelixirstatus 76

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Processes on the Erlang VM » not OS processes » extremely lightweight » 100K's processes » utilizes all CPU cores @nicholasjhenry, #myelixirstatus 77

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Explore concurrency in Elixir @nicholasjhenry, #myelixirstatus 78

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Let's look at our example @nicholasjhenry, #myelixirstatus 79

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defmodule FakeSearchEngine do def search(query) do result = case query do # {atom, query_time, text} "Ruby" -> {:ok, 100, "Ruby is a dynamic, reﬂective, object-oriented..."} "Python" -> {:ok, 2000, "Python is a widely used general-purpose, high-level..."} "Elixir" -> {:ok, 4000, "Elixir is a functional, concurrent, general-purpose..."} _ -> {:error, 10000, "Results not found" } end result = {_, query_time, _} :timer.sleep query_time result end end @nicholasjhenry, #myelixirstatus 80

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iex> FakeSearchEngine.search("Ruby") {:ok, 100, "Ruby is a dynamic, reﬂective, object-oriented..."} @nicholasjhenry, #myelixirstatus 81

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Challenge Run multiple searches concurrently ["Elixir", "Java", "Ruby"] @nicholasjhenry, #myelixirstatus 82

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What you need to know spawn(fn -> expression_1 #... expression_n end) @nicholasjhenry, #myelixirstatus 83

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iex> spawn(fn -> IO.inspect FakeSearchEngine.search("Ruby") end) @nicholasjhenry, #myelixirstatus 84

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iex> spawn(fn -> IO.inspect FakeSearchEngine.search("Ruby") end) #PID<0.100.0> @nicholasjhenry, #myelixirstatus 85

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iex> spawn(fn -> IO.inspect FakeSearchEngine.search("Ruby") end) #PID<0.100.0> {:ok, 100, "Ruby is a dynamic, reﬂective, object-oriented..."} @nicholasjhenry, #myelixirstatus 86

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Multiple searches sequentially @nicholasjhenry, #myelixirstatus 87

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Remember "each"? Ruby irb> a = [ "a", "b", "c" ] irb> a.each {|x| print "#{x} -- " } a -- b -- c -- => ["a", "b", "c"] Elixir iex> a = [ "a", "b", "c" ] iex> Enum.each(a, fn(x) -> IO.write "#{x} -- " end) a -- b -- c -- :ok @nicholasjhenry, #myelixirstatus 88

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iex> Enum.each(["Elixir", "Java", "Ruby"], fn(query) -> ...> IO.inspect FakeSearchEngine.search(query) ...> end) @nicholasjhenry, #myelixirstatus 89

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iex> Enum.each(["Elixir", "Java", "Ruby"], fn(query) -> ...> IO.inspect FakeSearchEngine.search(query) ...> end) {:ok, 4000, "Elixir is a functional, concurrent, general-purpose..."} {:error, 10000, "Results not found"} @nicholasjhenry, #myelixirstatus 91

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Multi Searches Concurrently @nicholasjhenry, #myelixirstatus 93

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iex> Enum.each(["Elixir", "Java", "Ruby"], fn(query) -> ...> spawn(fn -> IO.inspect FakeSearchEngine.search(query) end) ...> end) @nicholasjhenry, #myelixirstatus 94

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iex> Enum.each(["Elixir", "Java", "Ruby"], fn(query) -> ...> spawn(fn -> IO.inspect FakeSearchEngine.search(query) end) ...> end) :ok @nicholasjhenry, #myelixirstatus 95

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iex> Enum.each(["Elixir", "Java", "Ruby"], fn(query) -> ...> spawn(fn -> IO.inspect FakeSearchEngine.search(query) end) ...> end) :ok {:ok, 100, "Ruby is a dynamic, reﬂective, object-oriented..."} {:ok, 4000, "Elixir is a functional, concurrent, general-purpose..."} @nicholasjhenry, #myelixirstatus 97

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So, how has Elixir transformed how I think about concurrency? Now I spawn processes with the same ease and frequency as I instantiate objects in Ruby. @nicholasjhenry, #myelixirstatus 99

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Begin your own transformation 1. Watch "Think Different(ly)" by Dave Thomas 3 2. Work through the Elixir Guides 4 3. Start practicing on Exercism.io 5 5 http://exercism.io/ 4 http://elixir-lang.org/getting-started 3 http://bit.ly/think-diff @nicholasjhenry, #myelixirstatus 100

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Thank you! » Nicholas Henry » independent Ruby/Rails developer » @nicholasjhenry » http://blog.firsthand.ca » references will be posted along with a recording and slides @nicholasjhenry, #myelixirstatus 101