An introduction to Erlang, with an angle for Rubyists. Talk given at Christchurch Ruby in New Zealand on 20 June, 2013. Title page: Lavanderia (Sturdy) Body: Avenir (Black) Code: Monaco (Regular) Feel free to use the slides for anything you need. Please contact me if you would like the original Keynote files.

1. Erlang
@aupajo
github.com/aupajo
Thursday, 27 June 13

2. Thursday, 27 June 13

3. Thursday, 27 June 13

4. Thursday, 27 June 13

5. Thursday, 27 June 13

6. ✔ PUNS
Thursday, 27 June 13

7. WHY?
Thursday, 27 June 13

8. CONCURRENCY
Thursday, 27 June 13

9. SCALING
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10. ROBUSTNESS
AXD301 – 99.9999999%
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11. FUN!
Thursday, 27 June 13

12. WHAT’S IT USED
FOR?
Thursday, 27 June 13

13. Ericsson/T-Mobile/Motorola mobile networks
Amazon’s SimpleDB
Facebook’s Chat
Delicious
Heroku’s Routing Mesh
Riak (distributed database)
RabbitMQ (AMPQ messaging server)
CouchDB (document-oriented database)
MochiWeb (HTTP server)
Ejabberd (XMPP IM server)
Thursday, 27 June 13

14. A BRIEF INTRO…
Thursday, 27 June 13

15. 17.
FirstName.
"hello".
[104,101,108,108,111].
anAtom.
{joe, 1.95}.
integer
variable
string
list
atom
tuple
Thursday, 27 June 13

16. QUIZ!
X = 19.
Y = 11.
X = X + Y.
?
WHAT DOES THIS CODE DO?
(Hint: the “.” is equivalent to “;” in other languages.)
Thursday, 27 June 13

17. QUIZ!
X = 19.
Y = 11.
X = X + Y.
** exception error: no match of
right hand side value 30
WHAT DOES THIS CODE DO?
Thursday, 27 June 13

18. VARIABLES
CAN’T VARY
Thursday, 27 June 13

19. = ISN’T =
Thursday, 27 June 13

20. PATTERN-
MATCHING
Thursday, 27 June 13

21. X = 5+7.
Thursday, 27 June 13

22. X = 5+7.
Thursday, 27 June 13

23. X = 12.
Thursday, 27 June 13

24. X = 12.
“Hmm… X is unbound…”
Thursday, 27 June 13

25. X = 12.
“What can I do to make this
statement true?”
Thursday, 27 June 13

26. X
Thursday, 27 June 13

27. 12
Thursday, 27 June 13

28. 12 = 5+7.
Thursday, 27 June 13

29. 12 = 5+7.
Thursday, 27 June 13

30. 12 = 12.
Thursday, 27 June 13

31. 12 = 12.
“Yes! It matches!”
Thursday, 27 June 13

32. TUPLES
THE BUSINESS
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33. Point = {12, 45}.
{X,Y} = {12, 45}.
Thursday, 27 June 13

34. Person = {person,
{name, joe},
{height, 1.82},
{eyecolour, brown}}.
Thursday, 27 June 13

35. {person,
{name, Who},
{height, _},
{eyecolour, _}} = Person.
Thursday, 27 June 13

36. {person, {name, Who}, _, _} = Person.
Thursday, 27 June 13

37. {_, {_, Who}, _, _} = Person.
Thursday, 27 June 13

38. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

39. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

40. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

41. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

42. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

43. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

44. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

45. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

46. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

47. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

48. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

49. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

50. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

51. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

52. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

53. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
X ok X is ok
{X,Y,abc} {12,ok,abc}
X is 12,
Y is ok
{X,Y} {33,44,"word"} FAILS
{X,Y,X} {{abc,12},42,{abc, 12}}
X is {abc,12},
Y is 42
{X,Y,X} {nifty,42,true} FAILS
Thursday, 27 June 13

54. CLAUSES
Thursday, 27 June 13

55. area(rectangle, W, H) -> W * H.
area(rectangle, 10, 20). 200
Thursday, 27 June 13

56. area(rectangle, W, H) -> W * H;
area(circle, R) -> R * 3.14.
Thursday, 27 June 13

57. area(rectangle, 10, 30).
area(rectangle, W, H) -> W * H.
area(circle, R) -> R * 3.14.
“I recognize that!”
Thursday, 27 June 13

58. LISTS
Thursday, 27 June 13

59. [Head|Tail] = [a,b,c,d].
Head.
Tail.
a
[b,c,d]
Thursday, 27 June 13

60. [H|T] = "odd".
H.
T.
"o"
["d","d"]
Thursday, 27 June 13

61. N = 12.
List = [43, 10, 11, 8, 50].
Smaller = [X || X <- List, X < N].
Bigger = [X || X <- List, X > N].
Thursday, 27 June 13

62. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
[H|T] [a, b, c, d]
H is a
T is [b,c,d]
[{name,Who}|T]
[{name,joe},
{name,mike}]
Name is joe,
Y is {name,mike}
[H|T] [a]
H is a
T is []
[H|T] [] FAILS
Thursday, 27 June 13

63. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
[H|T] [a, b, c, d]
H is a
T is [b,c,d]
[{name,Who}|T]
[{name,joe},
{name,mike}]
Name is joe,
Y is {name,mike}
[H|T] [a]
H is a
T is []
[H|T] [] FAILS
Thursday, 27 June 13

64. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
[H|T] [a, b, c, d]
H is a
T is [b,c,d]
[{name,Who}|T]
[{name,joe},
{name,mike}]
Name is joe,
Y is {name,mike}
[H|T] [a]
H is a
T is []
[H|T] [] FAILS
Thursday, 27 June 13

65. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
[H|T] [a, b, c, d]
H is a
T is [b,c,d]
[{name,Who}|T]
[{name,joe},
{name,mike}]
Name is joe,
Y is {name,mike}
[H|T] [a]
H is a
T is []
[H|T] [] FAILS
Thursday, 27 June 13

66. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
[H|T] [a, b, c, d]
H is a
T is [b,c,d]
[{name,Who}|T]
[{name,joe},
{name,mike}]
Name is joe,
Y is {name,mike}
[H|T] [a]
H is a
T is []
[H|T] [] FAILS
Thursday, 27 June 13

67. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
[H|T] [a, b, c, d]
H is a
T is [b,c,d]
[{name,Who}|T]
[{name,joe},
{name,mike}]
Name is joe,
Y is {name,mike}
[H|T] [a]
H is a
T is []
[H|T] [] FAILS
Thursday, 27 June 13

68. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
[H|T] [a, b, c, d]
H is a
T is [b,c,d]
[{name,Who}|T]
[{name,joe},
{name,mike}]
Name is joe,
Y is {name,mike}
[H|T] [a]
H is a
T is []
[H|T] [] FAILS
Thursday, 27 June 13

69. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
[H|T] [a, b, c, d]
H is a
T is [b,c,d]
[{name,Who}|T]
[{name,joe},
{name,mike}]
Name is joe,
Y is {name,mike}
[H|T] [a]
H is a
T is []
[H|T] [] FAILS
Thursday, 27 June 13

70. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
[H|T] [a, b, c, d]
H is a
T is [b,c,d]
[{name,Who}|T]
[{name,joe},
{name,mike}]
Name is joe,
Y is {name,mike}
[H|T] [a]
H is a
T is []
[H|T] [] FAILS
Thursday, 27 June 13

71. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
[H|T] [a, b, c, d]
H is a
T is [b,c,d]
[{name,Who}|T]
[{name,joe},
{name,mike}]
Name is joe,
Y is {name,mike}
[H|T] [a]
H is a
T is []
[H|T] [] FAILS
Thursday, 27 June 13

72. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
[H|T] [a, b, c, d]
H is a
T is [b,c,d]
[{name,Who}|T]
[{name,joe},
{name,mike}]
Name is joe,
Y is {name,mike}
[H|T] [a]
H is a
T is []
[H|T] [] FAILS
Thursday, 27 June 13

73. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
[H|T] [a, b, c, d]
H is a
T is [b,c,d]
[{name,Who}|T]
[{name,joe},
{name,mike}]
Name is joe,
Y is {name,mike}
[H|T] [a]
H is a
T is []
[H|T] [] FAILS
Thursday, 27 June 13

74. QUIZ!
HOW DO THESE PATTERNS MATCH?
PATTERN TERM RESULT
[H|T] [a, b, c, d]
H is a
T is [b,c,d]
[{name,Who}|T]
[{name,joe},
{name,mike}]
Name is joe,
Y is {name,mike}
[H|T] [a]
H is a
T is []
[H|T] [] FAILS
Thursday, 27 June 13

75. SOLVING
PROBLEMS
Thursday, 27 June 13

76. cost(oranges) -> 5;
cost(apples) -> 2;
cost(pears) -> 9;
cost(milk) -> 7.
cost(milk). 7
Thursday, 27 June 13

77. ShoppingList = [
{oranges, 3},
{apples, 5},
{pears, 2},
{milk, 1}
].
total(ShoppingList).
Thursday, 27 June 13

78. [{oranges, 3},{apples, 5},…]
total([{Item, N}|T]) ->
cost(Item) * N + total(T);
total([]) -> [].
Thursday, 27 June 13

79. cheaperThan(Item, List) ->
[X || X <- List, cost(X) < cost(Item)].
Thursday, 27 June 13

80. qsort([]) -> [];
qsort([Pivot|T) ->
qsort([ X || X <- T, X < Pivot ])
++ [Pivot] ++
qsort([ X || X <- T, X >= Pivot ]).
Thursday, 27 June 13

81. PROCESSES
PROCESSES
PROCESSES
PROCESSES
PROCESSES
PROCESSES
PROCESSES
PROCESSES
PROCESSES
Thursday, 27 June 13

82. THE REAL WORLD
IS PARALLEL
Thursday, 27 June 13

83. PEOPLE ARE
INDEPENDENT
ENTITIES…
Thursday, 27 June 13

84. WHO
COMMUNICATE BY
SENDING
MESSAGES
Thursday, 27 June 13

85. Thursday, 27 June 13

86. Thursday, 27 June 13

87. Thursday, 27 June 13

88. Thursday, 27 June 13

89. Thursday, 27 June 13

90. INTERESTING
PROJECTS
Thursday, 27 June 13

91. Thursday, 27 June 13

92. Thursday, 27 June 13

93. Thursday, 27 June 13