Everything is Reduce

A presentation about the `Enum.reduce/3` function in Elixir.

Presented at:
- Elixir Girls workshop on 28 July 2017
- Sydney Elixir Meetup on 2 August 2017
- Elixir Camp 4 on 27 October 2018
- Culture Amp brownbag lunch meetup on 3 July 2019

Presentation slide deck markdown and speaker notes (useable in Deckset): https://github.com/paulfioravanti/presentations/tree/master/everything_is_reduce

Transcript

1. EVERYTHING IS reduce 1/75 — @paulfioravanti
2. THIS PRESENTATION IS ABOUT 2/75 — @paulfioravanti
3. THIS PRESENTATION IS ABOUT reduce 3/75 — @paulfioravanti
4. TRANSFORM SOMETHING 4/75 — @paulfioravanti
5. TRANSFORM TO A DIFFERENT FORM 5/75 — @paulfioravanti
6. TRANSFORM TO A MORE BASIC FORM 6/75 — @paulfioravanti
7. ! ➡ 7/75 — @paulfioravanti
8. def pulp( ! ) do " end 8/75 — @paulfioravanti
9. def pulp([ ! , , ]) do " end 9/75 — @paulfioravanti
10. def reduce([ ! , , ]) do " end 10/75 — @paulfioravanti
11. Enum 11/75 — @paulfioravanti
12. Lists [1, 2, 3] 12/75 — @paulfioravanti
13. Maps %{apple: " ! ", banana: " "} 13/75 — @paulfioravanti
14. So... 14/75 — @paulfioravanti
15. Enum.sum([1, 2, 3]) #=> 15/75 — @paulfioravanti
16. Enum.sum([1, 2, 3]) #=> 6 16/75 — @paulfioravanti
17. Enum.join(["Elixir", "is", "awesome!"], " ") #=> 17/75 — @paulfioravanti
18. Enum.join(["Elixir", "is", "awesome!"], " ") #=> "Elixir is awesome!" 18/75 — @paulfioravanti
19. [1, 2, 3] 19/75 — @paulfioravanti
20. PERFORM OPERATION 20/75 — @paulfioravanti
21. DERIVE INFORMATION 21/75 — @paulfioravanti
22. CREATE NEW INFORMATION 22/75 — @paulfioravanti
23. ! 23/75 — @paulfioravanti
24. [1, 2, 3] 24/75 — @paulfioravanti
25. Enum.each([1, 2, 3], fn number -> IO.puts("Current number is #{number}") end) #=> 25/75 — @paulfioravanti
26. Enum.each([1, 2, 3], fn number -> IO.puts("Current number is #{number}") end) Current number is 1 Current number is 2 Current number is 3 #=> :ok 26/75 — @paulfioravanti
27. [1, 2, 3] ⬇ :ok 27/75 — @paulfioravanti
28. [1, 2, 3] ⬇ :ok 28/75 — @paulfioravanti
29. [1, 2, 3] ⬇ [2, 4, 6] 29/75 — @paulfioravanti
30. Enum.map([1, 2, 3], fn number -> number * 2 end) #=> 30/75 — @paulfioravanti
31. Enum.map([1, 2, 3], fn number -> number * 2 end) #=> [2, 4, 6] 31/75 — @paulfioravanti
32. ! 32/75 — @paulfioravanti
33. [1, 2, 3] 33/75 — @paulfioravanti
34. ["a","b","c"] 34/75 — @paulfioravanti
35. ["a","a","a","b","c","c"] 35/75 — @paulfioravanti
36. ["a","a","a","b","c","c"] ⬇ %{"a" => 3,"b" => 1,"c" => 2} 36/75 — @paulfioravanti
37. Requirements → Take in a list → Return a map → Loop over each element in list → Add letter key to map if it doesn't exist → If letter key exists, increment its value 37/75 — @paulfioravanti
38. ["a","a","a","b","c","c"] ⬇ %{"a" => 3,"b" => 1,"c" => 2} 38/75 — @paulfioravanti
39. reduce 39/75 — @paulfioravanti
40. ! 40/75 — @paulfioravanti
41. Enum.reduce(enumerable, acc, fun) 41/75 — @paulfioravanti
42. Enum.reduce(["a", "a", "a", "b", "c", "c"], acc, fun) 42/75 — @paulfioravanti
43. list = ["a", "a", "a", "b", "c", "c"] Enum.reduce(list, acc, fun) 43/75 — @paulfioravanti
44. list = ["a", "a", "a", "b", "c", "c"] Enum.reduce(list, accumulator, fun) 44/75 — @paulfioravanti
45. list = ["a", "a", "a", "b", "c", "c"] Enum.reduce(list, acc, fun) 45/75 — @paulfioravanti
46. list = ["a", "a", "a", "b", "c", "c"] Enum.reduce(list, acc, fun) #=> %{"a" => 3, "b" => 1, "c" => 2} 46/75 — @paulfioravanti
47. list = ["a", "a", "a", "b", "c", "c"] Enum.reduce(list, %{}, fun) #=> %{"a" => 3, "b" => 1, "c" => 2} 47/75 — @paulfioravanti
48. list = ["a", "a", "a", "b", "c", "c"] Enum.reduce(list, %{"a" => 10}, fun) #=> %{"a" => 3, "b" => 1, "c" => 2} 48/75 — @paulfioravanti
49. list = ["a", "a", "a", "b", "c", "c"] Enum.reduce(list, %{}, fun) #=> %{"a" => 3, "b" => 1, "c" => 2} 49/75 — @paulfioravanti
50. list = ["a", "a", "a", "b", "c", "c"] Enum.reduce(list, %{}, fn char, map -> # ... # ... # ... end) #=> %{"a" => 3, "b" => 1, "c" => 2} 50/75 — @paulfioravanti
51. list = ["a", "a", "a", "b", "c", "c"] Enum.reduce(list, %{}, fn char, map -> Map.update(map, char, 1, fn value -> value + 1 end) end) #=> %{"a" => 3, "b" => 1, "c" => 2} 51/75 — @paulfioravanti
52. list = ["a", "a", "a", "b", "c", "c"] Enum.reduce(list, %{}, fn char, map -> Map.update(map, char, 1, fn value -> value + 1 end) end) #=> %{"a" => 3, "b" => 1, "c" => 2} 52/75 — @paulfioravanti
53. list = ["a", "a", "a", "b", "c", "c"] Enum.reduce(list, %{}, fn char, map -> Map.update(map, char, 1, fn value -> value + 1 end) end) #=> %{"a" => 3, "b" => 1, "c" => 2} 53/75 — @paulfioravanti
54. list = ["a", "a", "a", "b", "c", "c"] Enum.reduce(list, %{}, fn char, map -> Map.update(map, char, 1, fn value -> value + 1 end) end) #=> %{"a" => 3, "b" => 1, "c" => 2} 54/75 — @paulfioravanti
55. list = ["a", "a", "a", "b", "c", "c"] Enum.reduce(list, %{}, fn char, map -> Map.update(map, char, 1, fn value -> value + 1 end) end) #=> %{"a" => 3, "b" => 1, "c" => 2} 55/75 — @paulfioravanti
56. list = ["a", "a", "a", "b", "c", "c"] Enum.reduce(list, %{}, fn char, map -> Map.update(map, char, 1, fn value -> value + 1 end) end) #=> %{"a" => 3, "b" => 1, "c" => 2} 56/75 — @paulfioravanti
57. EVERY Enum FUNCTION IS reduce 57/75 — @paulfioravanti
58. Enum.map([1, 2, 3], fn number -> number * 2 end) #=> [2, 4, 6] 58/75 — @paulfioravanti
59. Enum.reduce([1, 2, 3], [], fn number, list -> [number * 2 | list] end) #=> 59/75 — @paulfioravanti
60. Enum.reduce([1, 2, 3], [], fn number, list -> [number * 2 | list] end) #=> [6, 4, 2] 60/75 — @paulfioravanti
61. Enum.reduce([1, 2, 3], [], fn number, list -> [number * 2 | list] end) |> Enum.reverse() #=> [2, 4, 6] 61/75 — @paulfioravanti
62. Enum.map([1, 2, 3], fn number -> number * 2 end) #=> [2, 4, 6] Enum.reduce([1, 2, 3], [], fn number, list -> [number * 2 | list] end) |> Enum.reverse() #=> [2, 4, 6] 62/75 — @paulfioravanti
63. SAME 63/75 — @paulfioravanti
64. Enum.each([1, 2, 3], fn number -> IO.puts("Current number is #{number}") end) Current number is 1 Current number is 2 Current number is 3 #=> :ok 64/75 — @paulfioravanti
65. Enum.reduce([1, 2, 3], nil, fn number, _acc -> IO.puts("Current number is #{number}") end) Current number is 1 Current number is 2 Current number is 3 #=> :ok 65/75 — @paulfioravanti
66. Enum.reduce([1, 2, 3], nil, fn number, _acc -> IO.puts("Current number is #{number}") end) Current number is 1 Current number is 2 Current number is 3 #=> :ok 66/75 — @paulfioravanti
67. Enum.reduce([1, 2, 3], nil, fn number, _acc -> IO.puts("Current number is #{number}") end) Current number is 1 Current number is 2 Current number is 3 #=> :ok 67/75 — @paulfioravanti
68. Enum.reduce([1, 2, 3], nil, fn number, _acc -> IO.puts("Current number is #{number}") end) Current number is 1 Current number is 2 Current number is 3 #=> :ok 68/75 — @paulfioravanti
69. Enum.each([1, 2, 3], fn number -> IO.puts("Current number is #{number}") end) Current number is 1 Current number is 2 Current number is 3 #=> :ok Enum.reduce([1, 2, 3], nil, fn number, _acc -> IO.puts("Current number is #{number}") end) Current number is 1 Current number is 2 Current number is 3 #=> :ok 69/75 — @paulfioravanti
70. SAME 70/75 — @paulfioravanti
71. ALL ARE FOR reduce 71/75 — @paulfioravanti
72. 72/75 — @paulfioravanti
73. ! 73/75 — @paulfioravanti
74. ! 74/75 — @paulfioravanti
75. Thanks! @paulfioravanti