Elixir in Elixir

https://www.codesync.global/speaker/jay-hayes/

Transcript

1. Metaprogramming Programs that Write Programs
2. InElixir Elixir
3. ElixirConf Orlando!
4. How to give the talk
5. 1. Set up the Topic
6. How much?
7. It depends™
8. What is “Elixir”?
9. Basics + STDLIB
10. of Elixir is written in Elixir 78%
11. of Elixir is written in Elixir 78% 87%
12. Compare to Ruby’s 44%
13. Numbers? Meh
14. if
15. def
16. |>
17. Metaprogramming
18. 2. Introductions
19. https://iamvery.com — @iamvery Jay Hayes
23. We’re hiring!
24. 3. Definitions
25. Metaprogramming
28. Code generation
29. Definition, plz
30. Metaprogramming
31. programming
32. Work on Data
33. 4 + 2
34. 4 + 2 data
35. 4 + 2 data func
36. +(4, 2)
37. Kernel. ( , ) 4 2 +
38. 4 2 +
39. 4 2 + # => 6
40. Meta…
41. The program is data
42. Programming the Program
43. Code generation
44. 4. Macros & Expressions
45. Macros
46. Macros are everywhere
47. good macros are invisible
48. defmodule ItTest do use ExUnit.Case test “works” do assert It.works? end end
49. defmodule ItTest do use ExUnit.Case test “works” do assert It.works? end end macros
50. What is the data?
51. What is the data? Program
52. defmodule ItTest do use ExUnit.Case test “works” do assert It.works? end end
53. defmodule ItTest do use ExUnit.Case test “works” do assert It.works? end end
54. defmodule ItTest do use ExUnit.Case test “works” do assert It.works? end end
55. defmodule ItTest do use ExUnit.Case test “works” do assert It.works? end end
56. defmodule ItTest do use ExUnit.Case test “works” do assert It.works? end end
57. defmodule ItTest do use ExUnit.Case test “works” do assert It.works? end end
58. defmodule ItTest do use ExUnit.Case test “works” do assert It.works? end end
59. Program macro Program ✨ ✨
60. Program macro Program ✨ ✨
61. Program macro Program ✨ ✨
62. Program macro Program Expression Expression ✨ ✨
63. Quoted expression?
64. Code Expressed as Data
65. {:+, [], [1, 2]}
66. Abstract Syntax Tree
67. / 1 + 2 3
68. / 1 + 2 3 / 1 + 2 3
69. ( ( )) / 1 + 2 3
70. ( ( )) / 1 + 2 3 func
71. ( ( )) / 1 + 2 3 func Args
72. ( ( )) / 1 + 2 3 func Args
73. 1 / ( 2 + 3 )
74. / 1 + 2 3
75. {: , …, [ , {: , …, [ , ]} / 1 + 2 3
76. {func, meta, args}
77. {func, meta, args} +(1, 2)
78. {:+, [], [1, 2]}
79. Back to macros…
80. Macros are Functions
81. Args are quoted
82. Args are quoted
83. (not evaluated)
84. Expression.match?(:lol > :wat) # => false Expression.match?(:lol = :wat) # => true
85. defmacro match?({:=, _, _}) do true end defmacro match?(_expr) do false end
86. Compile time
87. Expression.match?(:lol > :wat) Expression.match?(:lol = :wat)
88. false true
89. Must return quoted
90. Must return quoted
91. Code generation
92. defmacro badmatch do {:=, [], [:lol, :wat]} end
93. Expression.badmatch # (MatchError)
94. :lol = :wat # (MatchError)
95. Program macro Program Expression Expression ✨ ✨
96. 5. Quoting
97. {:+, [], [1, {:-, [], [2, 3]}]}
98. Quote/2
99. Easier to grok
100. Return AST of Expression
101. Return AST of Expression
102. {func, meta, args}
103. quote do :lol = :wat end
104. {:=, [], [:lol, :wat]}
105. quote do 1 / (2 + 3) end
106. {:/, [], [1, {:+, [2, 3]}
107. {:/, [], [1, {:+, [2, 3]}
108. ]} {:/, [], [1, {:+, [2, 3]}
109. Why “quote”?
110. Like strings…
111. Sort of…
112. “1+1”
113. eval “1+1”
114. eval “1+1” # => 2
115. quote(do: 1+1)
116. expr = quote(do: 1+1) Code.eval_quoted(expr)
117. expr = quote(do: 1+1) Code.eval_quoted(expr) # => {2, []}
118. Bonus:Syntax✔
119. Recursive
120. Terminal Values
121. Quoted Literals
122. 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]
123. 6. Unquoting
124. Value Injection
125. Unquote/1
126. Strings?
127. Like string interpolation
128. Sort of…
129. Inject value into quoted string
130. name = “Sue” “hi name” # => “hi name”
131. name = “Sue” “hi #{name}” # => “hi Sue”
132. Inject value into quoted Expression
133. num = 42 expr = quote do: 1 + num # => {:+, [], [1, {:num, [], :Elixir}]}
134. num = 42 expr = quote do: 1 + num # => {:+, [], [1, {:num, [], :Elixir}]} Code.eval_quoted(expr) # ERROR! `num` is undefined
135. num = 42 expr = quote do: 1 + unquote(num) # => {:+, [], [1, 42]}
136. num = 42 expr = quote do: 1 + unquote(num) # => {:+, [], [1, 42]} Code.eval_quoted(expr) # => {43, []}
137. num = 42 expr = “1 + #{num}” # => “1 + 42” eval expr # => 43
138. Inject value into quoted Expression
139. “It’s already quoted”
140. Expression Injection
141. one = quote do: 1 + 1 # => {:+, [], [1, 1]} two = quote do: 2 + 2 # => {:+, [], [2, 2]} sum = quote do: unquote(one) + unquote(two) # => {:+, [], [ # {:+, [], [1, 1]}, # {:+, [], [2, 2]} # ]}
142. Code.eval_quoted(sum) # => {6, []}
143. 7. Write a Macro
144. if
145. if foo > 0 do IO.puts(“Pass!”) else IO.puts(“Fail.”) end
146. if(…, do: …, else: …)
147. if(…, [do: …, else: …])
148. if(…, [do: …, else: …]) cond
149. if(…, [do: …, else: …]) cases cond
150. Truthy & Falsey
151. false || nil Falsey
152. Anything else Truthy
153. case … do x when x in [false, nil] -> … _ -> … end
154. case … do x when x in [false, nil] -> … _ -> … end cond
155. case … do x when x in [false, nil] -> … _ -> … end cond cases
156. 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
157. 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
158. 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 cases
159. 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
160. 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
161. 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 cases
162. 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
163. if do else end IO.puts(“Pass!”) IO.puts(“Fail.”) foo > 0
164. case do x when x in [false, nil] -> _ -> end IO.puts(“Pass!”) IO.puts(“Fail.”) foo > 0
165. 8. Wrap Up with Guidance
166. When to macro…
167. #1 Don’t
168. Write functions
169. import String defmacro adds(a, b) do quote do to_integer(unquote(a)) + to_integer(unquote(b)) end end
170. import String defmacro adds(a, b) do quote do to_integer(unquote(a)) + to_integer(unquote(b)) end end
171. import String def adds(a, b) do to_integer(a) + to_integer(b) end
172. Prefer direct solutions
173. Decision based on args
174. Transformation
175. Less error-prone
176. #2 Constants
177. defmodule Conversions do defmacro seconds_per_minute, do: 60 defmacro minutes_per_hour, do: 60 end
178. h/t module attrs @second_per_minute
179. #3 DSL
180. html do body do div class: “content” do p “Engaging content.” end end end
181. scope “/”, HelloWeb do pipe_through :browser get “/”, PageController, :index end
182. #4 Hide details
183. test “works” do assert It.works? end
184. #5 Reduce boilerplate
185. Language extension
186. defmodule Lolwat do def lol do :wat end end
187. :elixir_module.compile(Lolwat, {:def, [context: Elixir, import: Kernel], [{:lol, [context: Elixir], Elixir}, [do: :wat]]}, [], __ENV__)
188. :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: []})
191. 9. Self Promotion
192. bit.ly/ElixirMeta2
193. Questions? @iamvery
194. With love,