Elixir in Elixir

Metaprogramming doesn't have to be scary. Elixir does it really well. Let me show you...

Transcript

1. Elixir Elixir In
2. How much?
3. It depends
4. What is “Elixir”?
5. Basics + STDLIB
6. of Elixir is written in Elixir 78%
7. Compare to Ruby’s 44%
8. Numbers? Meh
9. if
10. def
11. |>
12. Metaprogramming
13. Code generation
14. +BZ
    )BZFT IUUQTJBNWFSZDPN
    n
    !JBNWFSZ
17. 8F
    EFWFMPQ
18. 8F
    UFBDI
19. 8F
    XSJUF
20. “I’m speaking at ElixirConf!”
21. “That’s nice. Where is it?”
22. “Orlando.”
23. “DISNEY IS THERE!!! CAN WE GO?!”
24. “Ya, actually it’s at Disney.”
25. “OMG!!! YOU’RE SPEAKING AT DISNEY?!!”
26. “Haha, sort of” *interrupted*
27. *on phone* “YA! He’s speaking at Disney!! We’re GOING!!!” *squeal*
30. Metaprogramming
32. programming Meta
33. Working on Data
34. data quantities on which operations are performed — Dictionary.app
35. 4 + 2 data
36. +(4, 2) data
37. Kernel.+(4, 2)
38. The program is data
39. Macros
40. Macros are everywhere
41. good macros are invisible
42. defmodule ItTest do use ExUnit.Case test “works” do assert It.works? end end macros
43. Where is the data? Program
44. defmodule ItTest do use ExUnit.Case test “works” do assert It.works? end end
45. defmodule ItTest do use ExUnit.Case test “works” do assert It.works? end end
46. defmodule ItTest do use ExUnit.Case test “works” do assert It.works? end end
47. defmodule ItTest do use ExUnit.Case test “works” do assert It.works? end end
48. Expression macro Expression ✨ ✨
49. Expression?
50. “Quoted” Elixir code
51. {func, …, args}
52. Abstract Syntax Tree
53. + 1 - 2 3
54. + 1 - 2 3 ( ( )) func Args
55. 1 + ( 2 - 3 )
56. Args are quoted
57. Expression.match?(:lol > :wat) # => false Expression.match?(:lol = :wat) # => true
58. defmacro match?({:=, _, _}) do true end defmacro match?(_expr) do false end
59. Expression.match?(:lol > :wat) # => false Expression.match?(:lol = :wat) # => true
60. false # => false true # => true
61. Must return quoted
62. defmacro badmatch do {:=, [], [:lol, :wat]} end
63. defmacro badmatch do quote do :lol = :wat end end
64. Expression.badmatch # (MatchError)
65. :lol = :wat # (MatchError)
66. Quote
67. {func, meta, args}
68. {:=, [], [:lol, :wat]}
69. quote do :lol = :wat end
70. Sort of like strings…
71. “1+1”
72. quote(do: 1+1)
73. quote do 1+1 end
74. Return AST of Expression
75. 2 - 3 quote do end
76. - 2 3 {: , […], [ , ]} (- 2 3)
77. quote do 1 + (2 - 3) end
78. {: , […], [ , {: , […], [ , ]}]} + 1 - 2 3 (+ 1 (- 2 3))
79. Easier to grok
80. {:+, […], [1, {:-, […], [2, 3]}]} quote do 1 + (2 - 3) end
81. Quoted Literals
82. quote do: “foo” # “foo” quote do: :foo # :foo quote do: 1 # 1 quote do: [1] # [1] quote do: {1,2} # {1,2} quote do: [a: 1] # [a: 1]
83. Unquote
84. “Inject value in quote”
85. Like string interpolation
86. “Inject value into quoted string”
87. name = “Sue” “hi name” # => “hi name”
88. name = “Sue” “hi #{name}” # => “hi Sue”
89. “Inject value into quoted Expression”
90. num = 42 # => 42 quote do: 1 + num # => {:+, [], [1, {:num, [], :Elixir}]}
91. num = 42 # => 42 quote do: 1 + unquote(num) # => {:+, [], [1, 42]}
92. name = “Sue” “hi #{name}” # => “hi Sue”
93. if
94. if foo > 0 do IO.puts(“Pass!”) else IO.puts(“Fail.”) end
95. if(…, do: …, else: …)
96. if(…, [do: …, else: …]) cases cond
97. Truthy & Falsey
98. false || nil Falsey
99. anything else Truthy
100. case … do x when x in [false, nil] -> … _ -> … end cond cases
101. defmacro if(c, do: tc, else: fc) do quote do case unquote(c) do x when x in [false, nil] -> unquote(fc) _ -> unquote(tc) end end end cond cases cond cases
102. if do else end foo > 0 IO.puts(“Pass!”) IO.puts(“Fail.”)
103. case do x when x in [false, nil] -> _ -> end foo > 0 IO.puts(“Fail.”) IO.puts(“Pass!”)
104. When to macro…
105. #1 Don’t
106. Write functions
107. defmacro add(a, b) do quote do unquote(a) + unquote(b) end end
108. def add(a, b) do a + b end
109. More direct
110. Less error-prone
111. #2 Constants
112. defmacro seconds_per_minute, do: 60 defmacro minutes_per_hour, do: 60
113. #3 DSL
114. html do body do div class: “content” do p “Engaging content.” end end end
115. #4 Hide details
116. test “works” do assert It.works? end
117. #5 Reduce boilerplate
118. Language extension
119. defmodule Lolwat do def lol do :wat end end
120. :elixir_module.compile(Lolwat, {:def, [context: Elixir, import: Kernel], [{:lol, [context: Elixir], Elixir}, [do: :wat]]}, [], __ENV__)
121. :elixir_module.compile(Lolwat, {:def, [context: Elixir, import: Kernel], [{:lol, [context: Elixir], Elixir}, [do: :wat]]}, [], %{__struct__: Macro.Env, aliases: [], context: nil, context_modules: [Mex], export_vars: nil, file: "iex", function: nil, functions: [Mex: [expand_all: 2], "IEx.Helpers": [c: 1, c: 2, cd: 1, clear: 0, flush: 0, h: 0, i: 1, l: 1, ls: 0, ls: 1, nl: 1, nl: 2, pid: 1, pid: 3, pwd: 0, r: 1, recompile: 0, respawn: 0, v: 0, v: 1], Kernel: [!=: 2, !==: 2, *: 2, +: 1, +: 2, ++: 2, -: 1, -: 2, --: 2, /: 2, <: 2, <=: 2, ==: 2, ===: 2, =~: 2, >: 2, >=: 2, abs: 1, apply: 2, apply: 3, binary_part: 3, bit_size: 1, byte_size: 1, div: 2, elem: 2, exit: 1, function_exported?: 3, get_and_update_in: 3, get_in: 2, hd: 1, inspect: 1, inspect: 2, is_atom: 1, is_binary: 1, is_bitstring: 1, is_boolean: 1, is_float: 1, is_function: 1, is_function: 2, is_integer: 1, is_list: 1, is_map: 1, is_number: 1, is_pid: 1, is_port: 1, is_reference: 1, is_tuple: 1, length: 1, macro_exported?: 3, make_ref: 0, map_size: 1, max: 2, min: 2, node: 0, node: 1, not: 1, pop_in: 2, put_elem: 3, put_in: 3, rem: 2, round: 1, self: 0, send: 2, spawn: 1, spawn: 3, spawn_link: 1, spawn_link: 3, spawn_monitor: 1, spawn_monitor: 3, struct: 1, struct: 2, struct!: 1, struct!: 2, throw: 1, tl: 1, trunc: 1, tuple_size: 1, update_in: 3]], lexical_tracker: nil, line: 2, macro_aliases: [], macros: [Mex: [mex: 1], "IEx.Helpers": [b: 1, h: 1, import_file: 1, import_file: 2, import_file_if_available: 1, import_if_available: 1, import_if_available: 2, s: 1, t: 1], Kernel: [!: 1, &&: 2, ..: 2, <>: 2, @: 1, alias!: 1, and: 2, binding: 0, binding: 1, def: 1, def: 2, defdelegate: 2, defexception: 1, defimpl: 2, defimpl: 3, defmacro: 1, defmacro: 2, defmacrop: 1, defmacrop: 2, defmodule: 2, defoverridable: 1, defp: 1, defp: 2, defprotocol: 2, defstruct: 1, destructure: 2, get_and_update_in: 2, if: 2, in: 2, is_nil: 1, match?: 2, or: 2, pop_in: 1, put_in: 2, raise: 1, raise: 2, reraise: 2, reraise: 3, sigil_C: 2, sigil_D: 2, sigil_N: 2, sigil_R: 2, sigil_S: 2, sigil_T: 2, sigil_W: 2, sigil_c: 2, sigil_r: 2, sigil_s: 2, sigil_w: 2, to_char_list: 1, to_charlist: 1, to_string: 1, unless: 2, update_in: 2, use: 1, use: 2, var!: 1, var!: 2, |>: 2, ||: 2]], module: nil, requires: [IEx.Helpers, Kernel, Kernel.Typespec, Mex], vars: []})
122. good macros are invisible
123. CJUMZ&MJYJS.FUB
124. !JBNWFSZ Questions?